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<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
<title>along101 个人博客</title>
<link href="/atom.xml" rel="self"/>
<link href="http://along101.site/"/>
<updated>2018-07-20T03:10:04.413Z</updated>
<id>http://along101.site/</id>
<author>
<name>along101</name>
</author>
<generator uri="http://hexo.io/">Hexo</generator>
<entry>
<title>springMvc Controller方法参数注解不被继承问题</title>
<link href="http://along101.site/2018/07/19/springMvc-controller-param/"/>
<id>http://along101.site/2018/07/19/springMvc-controller-param/</id>
<published>2018-07-19T14:20:13.000Z</published>
<updated>2018-07-20T03:10:04.413Z</updated>
<content type="html"><![CDATA[<h1 id="问题描述"><a href="#问题描述" class="headerlink" title="问题描述"></a>问题描述</h1><p>spring-cloud-openfeign 很方便的将http rest服务调用转换为基于接口的rpc调用。<br>服务端和客户端多引用相同的Rest定义接口，服务端使用RestController实现该接口，客户端通过Feign生成该接口的代理，就能保证服务端和客户端的协议。<br>但是springMvc有个缺陷，RestController继承的接口能将接口类和方法上的注解都继承过来，<strong>但是方法参数的注解却无法继承</strong>。<br>本文提供了一种解决该问题的方案，非侵入试的巧妙的解决了该问题。</p><a id="more"></a><h1 id="问题还原"><a href="#问题还原" class="headerlink" title="问题还原"></a>问题还原</h1><h2 id="hello-service-api"><a href="#hello-service-api" class="headerlink" title="hello-service-api"></a>hello-service-api</h2><p>首先新建一个公共接口工程<code>hello-service-api</code></p><blockquote><p>可以参考github：<a href="https://github.com/along101/spring-boot-test/tree/master/feign-test/hello-service-api" target="_blank" rel="noopener">hello-service-api</a></p></blockquote><p>新建两个公共的接口，包含springMvc注解：<br><code>HelloService1</code><br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping</span>(<span class="string">"/test1"</span>)</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">HelloService1</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="meta">@RequestMapping</span>(value = <span class="string">"/hello1"</span>, method = RequestMethod.GET)</span><br><span class="line"> <span class="function">String <span class="title">hello</span><span class="params">(@RequestParam(<span class="string">"name"</span>)</span> String name)</span>;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@RequestMapping</span>(value = <span class="string">"/hello2"</span>, method = RequestMethod.GET)</span><br><span class="line"> <span class="function">User <span class="title">hello</span><span class="params">(@RequestParam(<span class="string">"name"</span>)</span> String name, @<span class="title">RequestParam</span><span class="params">(<span class="string">"age"</span>)</span> Integer age)</span>;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@RequestMapping</span>(value = <span class="string">"/hello3"</span>, method = RequestMethod.POST)</span><br><span class="line"> <span class="function">String <span class="title">hello</span><span class="params">(@RequestBody User user)</span></span>;</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p><code>HelloService2</code><br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping</span>(<span class="string">"/test2"</span>)</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">HelloService2</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="meta">@RequestMapping</span>(value = <span class="string">"/hello1"</span>, method = RequestMethod.GET)</span><br><span class="line"> <span class="function">String <span class="title">hello</span><span class="params">(@RequestParam(<span class="string">"name"</span>)</span> String name)</span>;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@RequestMapping</span>(value = <span class="string">"/hello2"</span>, method = RequestMethod.GET)</span><br><span class="line"> <span class="function">User <span class="title">hello</span><span class="params">(@RequestParam(<span class="string">"name"</span>)</span> String name, @<span class="title">RequestParam</span><span class="params">(<span class="string">"age"</span>)</span> Integer a)</span>;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@RequestMapping</span>(value = <span class="string">"/hello3"</span>, method = RequestMethod.POST)</span><br><span class="line"> <span class="function">String <span class="title">hello</span><span class="params">(@RequestBody User user)</span></span>;</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><h2 id="hello-service-problem"><a href="#hello-service-problem" class="headerlink" title="hello-service-problem"></a>hello-service-problem</h2><p>新建spring boot工程<code>hello-service-problem</code>，依赖<code>hello-service-api</code></p><blockquote><p>可以参考github：<a href="https://github.com/along101/spring-boot-test/tree/master/feign-test/hello-service-problem" target="_blank" rel="noopener">hello-service-problem</a></p></blockquote><p>新建两个<code>RestController</code>，分别实现<code>HelloService1</code>、<code>HelloService2</code>两个接口。</p><p><code>HelloController1</code>，方法参数上没有加注解<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RestController</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">HelloController1</span> <span class="keyword">implements</span> <span class="title">HelloService1</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> String <span class="title">hello</span><span class="params">(String name)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="string">"Hello1 "</span> + name;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> User <span class="title">hello</span><span class="params">(String name, Integer a)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> User(name, a);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> String <span class="title">hello</span><span class="params">(User user)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="string">"Hello1 "</span> + user.getName() + <span class="string">", "</span> + user.getAge();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p><code>HelloController2</code>，方法参数上加了注解<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RestController</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">HelloController2</span> <span class="keyword">implements</span> <span class="title">HelloService2</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> String <span class="title">hello</span><span class="params">(@RequestParam(<span class="string">"name"</span>)</span> String name) </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="string">"Hello2 "</span> + name;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> User <span class="title">hello</span><span class="params">(@RequestParam(<span class="string">"name"</span>)</span> String name, @<span class="title">RequestParam</span><span class="params">(<span class="string">"age"</span>)</span> Integer a) </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> User(name, a);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> String <span class="title">hello</span><span class="params">(@RequestBody User user)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="string">"Hello2 "</span> + user.getName() + <span class="string">", "</span> + user.getAge();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>启动工程，在浏览器中输入url测试两个接口：</p><p><a href="http://localhost:8081/test1/hello2?name=along&age=12" target="_blank" rel="noopener">http://localhost:8081/test1/hello2?name=along&age=12</a><br>结果：<br><figure class="highlight json"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">{</span><br><span class="line"> <span class="attr">"name"</span>: <span class="string">"along"</span>,</span><br><span class="line"> <span class="attr">"age"</span>: <span class="literal">null</span></span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p><a href="http://localhost:8081/test2/hello2?name=along&age=12" target="_blank" rel="noopener">http://localhost:8081/test2/hello2?name=along&age=12</a><br>结果：<br><figure class="highlight json"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">{</span><br><span class="line"> <span class="attr">"name"</span>: <span class="string">"along"</span>,</span><br><span class="line"> <span class="attr">"age"</span>: <span class="number">12</span></span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>为什么第一个测试的name有值，而age为null呢？<br>我们看到<code>HelloController1.hello(String name, Integer a)</code>方法参数没有注解，因为没有注解，spring根据参数名称从请求参数中找值，name找到了，a没有找到，所有name有值，age为null。</p><p>第二个测试，<code>HelloController2.hello(@RequestParam("name") String name, @RequestParam("age") Integer a)</code>方法参数都有注解，spring就根据注解从请求参数中找值，都能找到，所有都不为空。</p><p>问题来了，我们继承了接口，接口方法参数上的注解没有继承过来，还要我们自己再写一遍，如果接口协议改了，实现类上的注解忘记改就悲剧了。</p><h1 id="思路"><a href="#思路" class="headerlink" title="思路"></a>思路</h1><p>问题是很明确了，如何解决呢？先看看springMvc原理，搞清楚一个请求过来，是如何反射到方法上的。</p><p>网上找到一个springMvc的原理图，描述的比较清晰：</p><p><img src="/2018/07/19/springMvc-controller-param/springMvc.png" alt=""></p><p>简单的描述下，几个核心类是<code>DispatcherServlet</code>、<code>HandlerMapping</code>、<code>HandlerAdapter</code>、<code>HandlerMethod</code>、<code>ModelAndView</code>、<code>ViewResolver</code>。</p><ul><li><code>DispatcherServlet</code> 处理请求的servlet，前端控制器，整个流程控制的中心，控制其它组件执行，统一调度</li><li><code>HandlerMapping</code> 处理映射器，根据请匹配处理器</li><li><code>HandlerAdapter</code> 处理适配器，将请求适配到处理器上</li><li><code>HandlerMethod</code> 具体的处理器，一般是Controller方法信息的封装</li><li><code>ModelAndView</code> 模型和视图，传递处理结果</li><li><code>ViewResolver</code> 视图解析器</li></ul><p>springMvc启动的时候，会通过配置或者扫描注解将这些核心类实例化，组装到<code>DispatcherServlet</code>中。</p><p>客户端发起请求springMvc主要处理的过程如下：</p><ol><li><code>DispatcherServlet</code>根据请求在所有的<code>HandlerMapping</code>中找到匹配的<code>HandlerMethod</code></li><li><code>DispatcherServlet</code>根据找到的<code>HandlerMethod</code>，找到所支持的<code>HandlerAdapter</code></li><li><code>HandlerAdapter</code>的主要实现类是<code>RequestMappingHandlerAdapter</code>，负责从request中解析<code>HandlerMethod</code>所需要的参数，然后反射调用<code>HandlerMethod</code>中的方法，再处理返回值封装为<code>ModelAndView</code>。</li><li>通过<code>ViewResolver</code>解析<code>ModelAndView</code>，处理请求返回</li></ol><p><code>HandlerMethod</code>中存放了调用发放的信息，属性有：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">HandlerMethod</span> </span>{</span><br><span class="line"></span><br><span class="line"><span class="comment">/** Logger that is available to subclasses */</span></span><br><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> Log logger = LogFactory.getLog(getClass());</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> Object bean;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> BeanFactory beanFactory;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> Class<?> beanType;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> Method method;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> Method bridgedMethod;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> MethodParameter[] parameters;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> HandlerMethod resolvedFromHandlerMethod;</span><br><span class="line">。。。</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>属性<code>MethodParameter[] parameters</code>是方法参数数组，存放每个方法参数的信息，包括参数注解。</p><p>springMvc就是根据<code>MethodParameter</code>从request中获取信息构造方法参数数组的。</p><p>既然springMvc没有将参数注解从父接口中集成过来，我们可以自己处理。</p><p>spring生命周期中的各个阶段，我们都可以进行扩展，那么，我们可以在spring bean装配完后，修改所有<code>HandlerMethod</code>中的<code>parameters</code>，找到所继承的接口重新填充就可以了。</p><h1 id="解决方案"><a href="#解决方案" class="headerlink" title="解决方案"></a>解决方案</h1><p>通过调试springMvc的源代码，spring启动时，将<code>HandlerMapping</code>的实现类<code>RequestMappingHandlerMapping</code>实例化为一个bean注册到Context中，通过<code>getHandlerMethods</code>方法可以获取到所有的<code>HandlerMethod</code>。</p><p>我们只要实现一个Bean的后置处理器，修改<code>RequestMappingHandlerMapping</code>中的所有<code>HandlerMethod</code>即可，代码如下：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">HandlerMappingPostProcessor</span> <span class="keyword">implements</span> <span class="title">BeanPostProcessor</span> </span>{</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> Object <span class="title">postProcessBeforeInitialization</span><span class="params">(Object bean, String beanName)</span> <span class="keyword">throws</span> BeansException </span>{</span><br><span class="line"> <span class="keyword">return</span> bean;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> Object <span class="title">postProcessAfterInitialization</span><span class="params">(Object bean, String beanName)</span> <span class="keyword">throws</span> BeansException </span>{</span><br><span class="line"> <span class="comment">//找到RequestMappingHandlerMapping</span></span><br><span class="line"> <span class="keyword">if</span> (RequestMappingHandlerMapping.class.isAssignableFrom(ClassUtils.getUserClass(bean))) {</span><br><span class="line"> RequestMappingHandlerMapping mapping = (RequestMappingHandlerMapping) bean;</span><br><span class="line"> <span class="comment">//获取所有的HandlerMethod</span></span><br><span class="line"> Map<RequestMappingInfo, HandlerMethod> maps = mapping.getHandlerMethods();</span><br><span class="line"> <span class="keyword">for</span> (HandlerMethod handlerMethod : maps.values()) {</span><br><span class="line"> <span class="comment">//获取所有的MethodParameter</span></span><br><span class="line"> MethodParameter[] parameters = handlerMethod.getMethodParameters();</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < parameters.length; i++) {</span><br><span class="line"> MethodParameter parameter = parameters[i];</span><br><span class="line"> Annotation[] parameterAnnotation = parameter.getParameterAnnotations();</span><br><span class="line"> <span class="comment">//找到接口方法</span></span><br><span class="line"> Method superMethod = findInterfaceMethod(parameter.getMethod());</span><br><span class="line"> <span class="keyword">if</span> (superMethod == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">continue</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//接口方法参数注解</span></span><br><span class="line"> Annotation[][] superMethodParameterAnnotations = superMethod.getParameterAnnotations();</span><br><span class="line"> Annotation[] superParameterAnnotation = superMethodParameterAnnotations[parameter.getParameterIndex()];</span><br><span class="line"> <span class="comment">//合并自身方法注解和接口方法注解，形成新的注解数组</span></span><br><span class="line"> Annotation[] newParameterAnnotation = <span class="keyword">new</span> Annotation[parameterAnnotation.length + superParameterAnnotation.length];</span><br><span class="line"> System.arraycopy(parameterAnnotation, <span class="number">0</span>, newParameterAnnotation, <span class="number">0</span>, parameterAnnotation.length);</span><br><span class="line"> System.arraycopy(superParameterAnnotation, <span class="number">0</span>, newParameterAnnotation, parameterAnnotation.length, superParameterAnnotation.length);</span><br><span class="line"> <span class="comment">//构造新的MethodParameter，由于SynthesizingMethodParameter参数没有公有的设置注解方法，只能新建一个</span></span><br><span class="line"> <span class="keyword">if</span> (parameter <span class="keyword">instanceof</span> SynthesizingMethodParameter) {</span><br><span class="line"> MethodParameter newParameter = <span class="keyword">new</span> NewHandlerMethodParameter((SynthesizingMethodParameter) parameter, newParameterAnnotation);</span><br><span class="line"> parameters[i] = newParameter;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> bean;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 找到方法实现的接口方法</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> method</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@return</span></span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="function"><span class="keyword">private</span> Method <span class="title">findInterfaceMethod</span><span class="params">(Method method)</span> </span>{</span><br><span class="line"> Set<Class<?>> interfaces = ClassUtils.getAllInterfacesForClassAsSet(method.getDeclaringClass());</span><br><span class="line"> <span class="keyword">for</span> (Class<?> superInterface : interfaces) {</span><br><span class="line"> Method superMethod = <span class="keyword">null</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> superMethod = superInterface.getMethod(method.getName(), method.getParameterTypes());</span><br><span class="line"> } <span class="keyword">catch</span> (NoSuchMethodException e) {</span><br><span class="line"> <span class="comment">//忽略异常</span></span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (superMethod != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">return</span> superMethod;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">null</span>;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>代码不多，注释也很清晰的描述了整个实现的逻辑，就是找到集成的接口方法，将接口方法的注解填充到<code>HandlerMethod</code>中。这里我们新建了一个<code>MethodParameter</code>的子类<code>NewHandlerMethodParameter</code>，源代码如下：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">NewHandlerMethodParameter</span> <span class="keyword">extends</span> <span class="title">SynthesizingMethodParameter</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">volatile</span> Annotation[] parameterAnnotations;</span><br><span class="line"> <span class="keyword">private</span> Annotation[] newParameterAnnotation;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="title">NewHandlerMethodParameter</span><span class="params">(SynthesizingMethodParameter original, Annotation[] newParameterAnnotation)</span> </span>{</span><br><span class="line"> <span class="keyword">super</span>(original);</span><br><span class="line"> <span class="keyword">this</span>.newParameterAnnotation = newParameterAnnotation;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 覆盖父类方法，返回合并接口注解的数组</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@return</span></span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="keyword">public</span> Annotation[] getParameterAnnotations() {</span><br><span class="line"> <span class="keyword">if</span> (<span class="keyword">this</span>.parameterAnnotations == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">this</span>.parameterAnnotations = adaptAnnotationArray(newParameterAnnotation);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">this</span>.parameterAnnotations;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>这里需要注意，我刚开始直继承<code>MethodParameter</code>，<code>getParameterAnnotations</code>方法直接返回<code>newParameterAnnotation</code>，是有问题的。<br>这里父类是<code>SynthesizingMethodParameter</code>，作用是使用方法<code>adaptAnnotationArray</code>将<code>newParameterAnnotation</code>进行改造，填充注解中属性<code>@AliasFor</code>的值。<br>如果没有这一步操作，会导致注解属性值不完整，比如<code>@RequestParam</code>中的<code>value</code>和<code>name</code>只填写了一个，语义上另外一个值是相同的。<br>实现原理是调用<code>AnnotationUtils.synthesizeAnnotation</code>方法，构造一个注解接口（注解实际上是接口）的新的动态代理对象，根据<code>@AliasFor</code>设置指定方法返回值。</p><p>新建spring-boot工程<code>hello-service</code>，将<code>HandlerMappingPostProcessor</code>注册为spring bean，复制<code>hello-service-problem</code>中的两个Controller</p><blockquote><p>可以参考github：<a href="https://github.com/along101/spring-boot-test/tree/master/feign-test/hello-service" target="_blank" rel="noopener">hello-service</a></p></blockquote><p>再启动spring-boot工程进在浏览器中输入url测试两个接口：</p><p><a href="http://localhost:8082/test1/hello2?name=along&age=12" target="_blank" rel="noopener">http://localhost:8082/test1/hello2?name=along&age=12</a><br>结果：<br><figure class="highlight json"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">{</span><br><span class="line"> <span class="attr">"name"</span>: <span class="string">"along"</span>,</span><br><span class="line"> <span class="attr">"age"</span>: <span class="number">12</span></span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p><a href="http://localhost:8082/test2/hello2?name=along&age=12" target="_blank" rel="noopener">http://localhost:8082/test2/hello2?name=along&age=12</a><br>结果：<br><figure class="highlight json"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">{</span><br><span class="line"> <span class="attr">"name"</span>: <span class="string">"along"</span>,</span><br><span class="line"> <span class="attr">"age"</span>: <span class="number">12</span></span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>问题解决了。</p>]]></content>
<summary type="html">
<h1 id="问题描述"><a href="#问题描述" class="headerlink" title="问题描述"></a>问题描述</h1><p>spring-cloud-openfeign 很方便的将http rest服务调用转换为基于接口的rpc调用。<br>服务端和客户端多引用相同的Rest定义接口，服务端使用RestController实现该接口，客户端通过Feign生成该接口的代理，就能保证服务端和客户端的协议。<br>但是springMvc有个缺陷，RestController继承的接口能将接口类和方法上的注解都继承过来，<strong>但是方法参数的注解却无法继承</strong>。<br>本文提供了一种解决该问题的方案，非侵入试的巧妙的解决了该问题。</p>
</summary>
<category term="spring" scheme="http://along101.site/categories/spring/"/>
<category term="spring" scheme="http://along101.site/tags/spring/"/>
<category term="rest" scheme="http://along101.site/tags/rest/"/>
</entry>
<entry>
<title>拍拍贷微服务rpc框架--raptor</title>
<link href="http://along101.site/2018/07/18/raptor-rpc/"/>
<id>http://along101.site/2018/07/18/raptor-rpc/</id>
<published>2018-07-18T19:16:13.000Z</published>
<updated>2018-07-20T03:10:04.409Z</updated>
<content type="html"><![CDATA[<h1 id="说明"><a href="#说明" class="headerlink" title="说明"></a>说明</h1><p>这是我在拍拍贷负责开发的微服务RPC框架，已经拍拍贷全面推广，生产稳定运行。</p><p>该RPC框架参考、借鉴了大量已有rpc框架的设计，主要特性如下：</p><ol><li>契约驱动(Contract-First)开发模式，采用protobuf契约，自动生成服务器端接口和客户端代码</li><li>基于HTTP协议，一套组件同时覆盖内部服务开发和对外开放场景</li><li>RPC/REST混合模式，既可以使用客户端以RPC/HTTP/JSON方式调用，也可以通过浏览器以REST/HTTP/JSON方式调用</li><li>支持多种强类型客户端自动生成，Java/C#/Python/iOS/Android…</li><li>设计实现简单轻量，依赖少，可以和Spring(Boot)无缝集成</li></ol><p>该框架已经开源，源码地址: <a href="https://github.com/ppdai-incubator/raptor" target="_blank" rel="noopener">https://github.com/ppdai-incubator/raptor</a></p><p>详细参考文档请参考: <a href="https://github.com/ppdai-incubator/raptor/wiki" target="_blank" rel="noopener">https://github.com/ppdai-incubator/raptor/wiki</a></p>]]></content>
<summary type="html">
<h1 id="说明"><a href="#说明" class="headerlink" title="说明"></a>说明</h1><p>这是我在拍拍贷负责开发的微服务RPC框架，已经拍拍贷全面推广，生产稳定运行。</p>
<p>该RPC框架参考、借鉴了大量已有rpc框架的设计
</summary>
<category term="微服务" scheme="http://along101.site/categories/%E5%BE%AE%E6%9C%8D%E5%8A%A1/"/>
<category term="微服务" scheme="http://along101.site/tags/%E5%BE%AE%E6%9C%8D%E5%8A%A1/"/>
<category term="rpc" scheme="http://along101.site/tags/rpc/"/>
<category term="契约驱动" scheme="http://along101.site/tags/%E5%A5%91%E7%BA%A6%E9%A9%B1%E5%8A%A8/"/>
</entry>
<entry>
<title>java 线程池原理</title>
<link href="http://along101.site/2018/07/18/java-threadpool/"/>
<id>http://along101.site/2018/07/18/java-threadpool/</id>
<published>2018-07-18T14:30:57.000Z</published>
<updated>2018-07-20T03:10:04.409Z</updated>
<content type="html"><![CDATA[<h1 id="线程生命周期及状态转换"><a href="#线程生命周期及状态转换" class="headerlink" title="线程生命周期及状态转换"></a>线程生命周期及状态转换</h1><p>我们先来看看java中线程的生命周期，已经各个状态之间的转换，用一张图能比较清晰的描述：</p><p><img src="/2018/07/18/java-threadpool/thread-status.png" alt=""></p><a id="more"></a><p>java中线程的状态一共分为6种：new、runnable、blocked、waiting、timed_waiting、terminated</p><h2 id="初始态：new"><a href="#初始态：new" class="headerlink" title="初始态：new"></a>初始态：new</h2><p>创建一个<code>Thread</code>对象，但还未调用<code>start()</code>启动线程时，线程处于初始态。</p><h2 id="运行态：runnable"><a href="#运行态：runnable" class="headerlink" title="运行态：runnable"></a>运行态：runnable</h2><p>在Java中，运行态包括<code>就绪态</code>和<code>运行态</code>。</p><ul><li>就绪态<ul><li>该状态下的线程已经获得执行所需的所有资源，只要CPU分配执行权就能运行。</li><li>所有就绪态的线程存放在就绪队列中。</li></ul></li><li>运行态<ul><li>获得CPU执行权，正在执行的线程。</li><li>由于一个CPU同一时刻只能执行一条线程，因此每个CPU每个时刻只有一条运行态的线程。</li></ul></li></ul><h2 id="阻塞态：blocked"><a href="#阻塞态：blocked" class="headerlink" title="阻塞态：blocked"></a>阻塞态：blocked</h2><ul><li>当一条正在执行的线程请求某一资源失败时，就会进入阻塞态。</li><li>而在Java中，阻塞态专指请求锁失败时进入的状态。</li><li>由一个阻塞队列存放所有阻塞态的线程。</li><li>处于阻塞态的线程会不断请求资源，一旦请求成功，就会进入就绪队列，等待执行。</li></ul><p>PS：锁、IO、Socket等都资源。</p><h2 id="等待：waiting"><a href="#等待：waiting" class="headerlink" title="等待：waiting"></a>等待：waiting</h2><ul><li>当前线程中调用wait、join、park函数时，当前线程就会进入等待态。</li><li>也有一个等待队列存放所有等待态的线程。</li><li>线程处于等待态表示它需要等待其他线程的指示才能继续运行。</li><li>进入等待态的线程会释放CPU执行权，并释放资源（如：锁）</li></ul><h2 id="超时等待：timed-waiting"><a href="#超时等待：timed-waiting" class="headerlink" title="超时等待：timed_waiting"></a>超时等待：timed_waiting</h2><ul><li>当运行中的线程调用<code>sleep(time)</code>、<code>wait(time)</code>、<code>join</code>、<code>parkNanos</code>、<code>parkUntil</code>时，就会进入该状态；</li><li>它和等待态一样，并不是因为请求不到资源，而是主动进入，并且进入后需要其他线程唤醒；</li><li>进入该状态后释放CPU执行权和占有的资源。</li><li>与等待态的区别：到了超时时间后自动进入阻塞队列，开始竞争锁。</li></ul><h2 id="终止：terminated"><a href="#终止：terminated" class="headerlink" title="终止：terminated"></a>终止：terminated</h2><p>线程执行结束后的状态。</p><h2 id="注意"><a href="#注意" class="headerlink" title="注意"></a>注意</h2><ul><li><code>wait()</code>方法会释放CPU执行权 和 占有的锁。</li><li><code>sleep(long)</code>方法仅释放CPU使用权，锁仍然占用；线程被放入超时等待队列，与<code>yield</code>相比，它会使线程较长时间得不到运行。</li><li><code>yield()</code>方法仅释放CPU执行权，锁仍然占用，线程会被放入就绪队列，会在短时间内再次执行。</li><li><code>wait</code>和<code>notify</code>必须配套使用，即必须使用同一把锁调用；</li><li><code>wait</code>和<code>notify</code>必须放在一个同步块中</li><li>调用<code>wait</code>和<code>notify</code>的对象必须是他们所处同步块的锁对象。</li></ul><h1 id="线程池的工作原理"><a href="#线程池的工作原理" class="headerlink" title="线程池的工作原理"></a>线程池的工作原理</h1><p>java线程池的核心类是<code>java.util.concurrent.ThreadPoolExecutor</code>，构造函数：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="title">ThreadPoolExecutor</span><span class="params">(<span class="keyword">int</span> corePoolSize, //核心线程的数量</span></span></span><br><span class="line"><span class="function"><span class="params"> <span class="keyword">int</span> maximumPoolSize, //最大线程数量</span></span></span><br><span class="line"><span class="function"><span class="params"> <span class="keyword">long</span> keepAliveTime, //超出核心线程数量以外的线程空余存活时间</span></span></span><br><span class="line"><span class="function"><span class="params"> TimeUnit unit, //存活时间的单位</span></span></span><br><span class="line"><span class="function"><span class="params"> BlockingQueue<Runnable> workQueue, //保存待执行任务的队列</span></span></span><br><span class="line"><span class="function"><span class="params"> ThreadFactory threadFactory, //创建新线程使用的工厂</span></span></span><br><span class="line"><span class="function"><span class="params"> RejectedExecutionHandler handler // 当任务无法执行时的处理器</span></span></span><br><span class="line"><span class="function"><span class="params"> )</span> </span>{</span><br><span class="line"> 。。。</span><br><span class="line"> }</span><br></pre></td></tr></table></figure></p><p>参数介绍如注释所示，要了解这些参数左右着什么，就需要了解线程池具体的执行方法<code>ThreadPoolExecutor.execute</code>:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">execute</span><span class="params">(Runnable command)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (command == <span class="keyword">null</span>)</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> NullPointerException();</span><br><span class="line"> <span class="keyword">int</span> c = ctl.get();</span><br><span class="line"> <span class="comment">//1.当前池中线程比核心数少，新建一个线程执行任务</span></span><br><span class="line"> <span class="keyword">if</span> (workerCountOf(c) < corePoolSize) {</span><br><span class="line"> <span class="keyword">if</span> (addWorker(command, <span class="keyword">true</span>))</span><br><span class="line"> <span class="keyword">return</span>;</span><br><span class="line"> c = ctl.get();</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//2.核心池已满，但任务队列未满，添加到队列中</span></span><br><span class="line"> <span class="keyword">if</span> (isRunning(c) && workQueue.offer(command)) {</span><br><span class="line"> <span class="keyword">int</span> recheck = ctl.get();</span><br><span class="line"> <span class="comment">////如果这时被关闭了，拒绝任务</span></span><br><span class="line"> <span class="keyword">if</span> (! isRunning(recheck) && remove(command))</span><br><span class="line"> reject(command);</span><br><span class="line"> <span class="comment">//如果之前的线程已被销毁完，新建一个线程</span></span><br><span class="line"> <span class="keyword">else</span> <span class="keyword">if</span> (workerCountOf(recheck) == <span class="number">0</span>)</span><br><span class="line"> addWorker(<span class="keyword">null</span>, <span class="keyword">false</span>);</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//3.核心池已满，队列已满，试着创建一个新线程</span></span><br><span class="line"> <span class="keyword">else</span> <span class="keyword">if</span> (!addWorker(command, <span class="keyword">false</span>))</span><br><span class="line"> reject(command);</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>可以看到，线程池处理一个任务主要分三步处理，代码注释里已经介绍了，我再用通俗易懂的例子解释一下：</p><p>（线程比作员工，<code>ThreadPoolExecutor</code>比作团队领导，核心池比作团队中编制员工数，核心池外的比作外包员工）</p><ol><li><p>有了新需求，先看有没有空闲的编制，有的话就招一个编制人员来做</p><blockquote><p>有点奇怪，为啥不利用现有空闲的编制员工？领导可能觉得先把人招满，有资源不用白不用</p></blockquote></li><li><p>如果编制人员已经满了，领导就把任务放到任务列表里面，编制人员自己去取任务干活</p><blockquote><p>编制员工都很自觉，盯着领导手上的任务，干完手头上的活立马去抢，都是好员工</p></blockquote></li><li><p>如果任务列表满了，活太多编制员工干不完了，领导就会去招外包来干</p><blockquote><p>虽然是外包，也很主动，干完手头上的活也去抢领导的手上的任务，悲哀的是，领导手上没有任务了，外包就自己走了，真是良心外包<br>我做外包这么多年，虽然很主动，但是赖着不走，多算人员多要钱</p></blockquote></li><li><p>外包也有限制，外包都到限制了，那没有办法，就要拒绝需求了</p><blockquote><p>需求不是你想拒绝就拒绝的，产品经理不同意怎么办？开会协商定策略吧。</p></blockquote></li></ol><p>结合这张图，应该能明白：</p><p><img src="/2018/07/18/java-threadpool/thread-pool.png" alt=""></p><p>前面提到的<code>ThreadPoolExecutor</code>构造函数的参数，分别影响以下内容：</p><ul><li><p><code>int corePoolSize</code>：核心线程池数量 </p><ul><li>在线程数少于核心数量时，有新任务进来就新建一个线程，即使有的线程没事干</li><li>等超出核心数量后，就不会新建线程了，空闲的线程就得去任务队列里取任务执行了<blockquote><p>编制员工</p></blockquote></li></ul></li><li><p><code>int maximumPoolSize</code>：最大线程数量 </p><ul><li>包括核心线程池数量 + 核心以外的数量</li><li>如果任务队列满了，并且池中线程数小于最大线程数，会再创建新的线程执行任务<blockquote><p>外包员工</p></blockquote></li></ul></li><li><p><code>long keepAliveTime</code>：核心池以外的线程存活时间，即没有任务的外包的存活时间 </p><ul><li>如果给线程池设置<code>allowCoreThreadTimeOut(true)</code>，则核心线程在空闲时头上也会响起死亡的倒计时</li><li>如果任务是多而容易执行的，可以调大这个参数，那样线程就可以在存活的时间里有更大可能接受新任务<blockquote><p>外包员工比较惨，没事干了，就得滚蛋，卸磨杀驴啊<br>编制员工好多了，不过领导心情不好，没事干了，核心员工也得滚蛋</p></blockquote></li></ul></li><li><p><code>BlockingQueue<Runnable> workQueue</code>：保存待执行任务的阻塞队列 </p><ul><li>不同的任务类型有不同的选择，下一小节介绍<blockquote><p>领导手上的任务表</p></blockquote></li></ul></li><li><p><code>ThreadFactory threadFactory</code>：每个线程创建的地方 </p><ul><li>可以给线程起个好听的名字，设置个优先级啥的</li></ul></li><li><p><code>RejectedExecutionHandler handler</code>：饱和策略，大家都很忙，咋办呢，有四种策略 </p><ul><li><code>CallerRunsPolicy</code>：只要线程池没关闭，直接用调用者所在线程来运行任务，就是你自己干</li><li><code>AbortPolicy</code>：直接抛出<code>RejectedExecutionException</code>异常</li><li><code>DiscardPolicy</code>：悄悄把任务放生，不做了</li><li><code>DiscardOldestPolicy</code>：把队列里待最久的那个任务扔了，然后再调用<code>execute()</code>试试看能行不</li><li>我们也可以实现自己的<code>RejectedExecutionHandler</code>接口自定义策略，比如调用<code>workQueue.put</code>方法阻塞住，需求方一直等着，只要团队有空就提需求</li></ul></li></ul><h2 id="阻塞队列-workQueue"><a href="#阻塞队列-workQueue" class="headerlink" title="阻塞队列 workQueue"></a>阻塞队列 workQueue</h2><p>当线程池中的核心线程数已满时，任务就要保存到队列中了。</p><p>线程池中使用的队列是<code>BlockingQueue</code>接口，常用的实现有如下几种：</p><ul><li><p><code>ArrayBlockingQueue</code>：基于数组、有界，按FIFO（先进先出）原则对元素进行排序</p></li><li><p><code>LinkedBlockingQueue</code>：基于链表，按FIFO（先进先出） 排序元素 </p><ul><li>吞吐量通常要高于<code>ArrayBlockingQueue</code></li><li><code>Executors.newFixedThreadPool()</code> 使用了这个队列</li></ul></li><li><p><code>SynchronousQueue</code>：不存储元素的阻塞队列 </p><ul><li>每个插入操作必须等到另一个线程调用移除操作，否则插入操作一直处于阻塞状态</li><li>吞吐量通常要高于<code>LinkedBlockingQueue</code></li><li><code>Executors.newCachedThreadPool</code>使用了这个队列</li></ul></li><li><p><code>PriorityBlockingQueue</code>：具有优先级的、无限阻塞队列</p></li></ul><h2 id="Executors-工厂创建线程池"><a href="#Executors-工厂创建线程池" class="headerlink" title="Executors 工厂创建线程池"></a>Executors 工厂创建线程池</h2><h3 id="newFixedThreadPool"><a href="#newFixedThreadPool" class="headerlink" title="newFixedThreadPool"></a>newFixedThreadPool</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> ExecutorService <span class="title">newFixedThreadPool</span><span class="params">(<span class="keyword">int</span> nThreads, ThreadFactory threadFactory)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> ThreadPoolExecutor(nThreads, nThreads,</span><br><span class="line"> <span class="number">0L</span>, TimeUnit.MILLISECONDS,</span><br><span class="line"> <span class="keyword">new</span> LinkedBlockingQueue<Runnable>(),</span><br><span class="line"> threadFactory);</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>不招外包，有固定数量核心成员的正常互联网团队。</p><p>可以看到，<code>FixedThreadPool</code>的核心线程数和最大线程数都是指定值，也就是说当线程池中的线程数超过核心线程数后，任务都会被放到阻塞队列中。</p><p>而这里选用的阻塞队列是<code>LinkedBlockingQueue</code>，使用的是默认容量<code>Integer.MAX_VALUE</code>，相当于没有上限。</p><blockquote><p>这个坑比较大，千万要注意，阿里巴巴java开发手册明确提醒，不能直接使用Executors</p></blockquote><h3 id="newSingleThreadExecutor"><a href="#newSingleThreadExecutor" class="headerlink" title="newSingleThreadExecutor"></a>newSingleThreadExecutor</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> ExecutorService <span class="title">newSingleThreadExecutor</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> FinalizableDelegatedExecutorService</span><br><span class="line"> (<span class="keyword">new</span> ThreadPoolExecutor(<span class="number">1</span>, <span class="number">1</span>,</span><br><span class="line"> <span class="number">0L</span>, TimeUnit.MILLISECONDS,</span><br><span class="line"> <span class="keyword">new</span> LinkedBlockingQueue<Runnable>()));</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>不招外包，只有一个核心成员的创业团队。</p><p>从参数可以看出来，<code>SingleThreadExecutor</code>相当于参数为1的<code>FixedThreadPool</code>。</p><h3 id="newCachedThreadPool"><a href="#newCachedThreadPool" class="headerlink" title="newCachedThreadPool"></a>newCachedThreadPool</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> ExecutorService <span class="title">newCachedThreadPool</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> ThreadPoolExecutor(<span class="number">0</span>, Integer.MAX_VALUE,</span><br><span class="line"> <span class="number">60L</span>, TimeUnit.SECONDS,</span><br><span class="line"> <span class="keyword">new</span> SynchronousQueue<Runnable>());</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>全部外包，没活最多待60秒的外包团队。</p><p>可以看到，<code>CachedThreadPool</code>没有核心线程，非核心线程数无上限，也就是全部使用外包，但是每个外包空闲的时间只有60秒，超过后就会被回收。</p><p><code>CachedThreadPool</code>使用的队列是<code>SynchronousQueue</code>，这个队列的作用就是传递任务，并不会保存。</p><p>因此当提交任务的速度大于处理任务的速度时，每次提交一个任务，就会创建一个线程。极端情况下会创建过多的线程，耗尽CPU和内存资源。</p><h3 id="newScheduledThreadPool"><a href="#newScheduledThreadPool" class="headerlink" title="newScheduledThreadPool"></a>newScheduledThreadPool</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> ScheduledExecutorService <span class="title">newScheduledThreadPool</span><span class="params">(<span class="keyword">int</span> corePoolSize)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> ScheduledThreadPoolExecutor(corePoolSize);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="title">ScheduledThreadPoolExecutor</span><span class="params">(<span class="keyword">int</span> corePoolSize)</span> </span>{</span><br><span class="line"> <span class="keyword">super</span>(corePoolSize, Integer.MAX_VALUE, <span class="number">0</span>, NANOSECONDS,</span><br><span class="line"> <span class="keyword">new</span> DelayedWorkQueue());</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>定期维护的 2B 业务团队，核心与外包成员都有。</p><p><code>ScheduledThreadPoolExecutor</code>继承自<code>ThreadPoolExecutor</code>， 最多线程数为<code>Integer.MAX_VALUE</code>，使用<code>DelayedWorkQueue</code>作为任务队列。</p><p><code>ScheduledThreadPoolExecutor</code>添加任务和执行任务的机制与<code>ThreadPoolExecutor</code>有所不同。</p><p><code>ScheduledThreadPoolExecutor</code>添加任务提供了另外两个方法：</p><ul><li><code>scheduleAtFixedRate()</code>：按某种速率周期执行</li><li><code>scheduleWithFixedDelay()</code>：在某个延迟后执行</li></ul><h2 id="提交任务的方法"><a href="#提交任务的方法" class="headerlink" title="提交任务的方法"></a>提交任务的方法</h2><p><code>ExecutorService</code>提供了两种提交任务的方法：</p><ol><li><code>execute()</code>：提交不需要返回值的任务</li><li><code>submit()</code>：提交需要返回值的任务</li></ol><h2 id="关闭线程池"><a href="#关闭线程池" class="headerlink" title="关闭线程池"></a>关闭线程池</h2><p>线程池即使不执行任务也会占用一些资源，所以在我们要退出任务时最好关闭线程池。</p><p>有两个方法关闭线程池：</p><ol><li><p><code>shutdown()</code></p><ul><li>将线程池的状态设置为 SHUTDOWN，并不会立即停止</li><li>停止接收外部submit的任务</li><li>内部正在跑的任务和队列里等待的任务，会执行完</li><li>等到上一步完成后，才真正停止</li></ul></li><li><p><code>shutdownNow()</code></p><ul><li>将线程池设置为STOP，企图立即停止</li><li>跟<code>shutdown()</code>一样，先停止接收外部提交的任务</li><li>忽略队列里等待的任务</li><li>尝试将正在跑的任务<code>interrupt</code>中断</li><li>返回未执行的任务列表</li></ul></li></ol><h2 id="等待线程结束"><a href="#等待线程结束" class="headerlink" title="等待线程结束"></a>等待线程结束</h2><p><code>awaitTermination</code>当前线程阻塞，直到</p><pre><code>- 等所有已提交的任务（包括正在跑的和队列中等待的）执行完- 或者等超时时间到- 或者线程被中断，抛出`InterruptedException`</code></pre><blockquote><p>优雅的关闭线程池，一般用<code>shutdown()</code>+<code>awaitTermination()</code></p></blockquote><h1 id="源代码分析"><a href="#源代码分析" class="headerlink" title="源代码分析"></a>源代码分析</h1><p>前面已经描述的很清楚了，再去看源代码就很容易，不在这里写了。</p>]]></content>
<summary type="html">
<h1 id="线程生命周期及状态转换"><a href="#线程生命周期及状态转换" class="headerlink" title="线程生命周期及状态转换"></a>线程生命周期及状态转换</h1><p>我们先来看看java中线程的生命周期，已经各个状态之间的转换，用一张图能比较清晰的描述：</p>
<p><img src="/2018/07/18/java-threadpool/thread-status.png" alt=""></p>
</summary>
<category term="java" scheme="http://along101.site/categories/java/"/>
<category term="java" scheme="http://along101.site/tags/java/"/>
<category term="thread" scheme="http://along101.site/tags/thread/"/>
</entry>
<entry>
<title>java8 reactor模式的实现之CompletableFuture</title>
<link href="http://along101.site/2018/07/17/java8-CompleteableFuture/"/>
<id>http://along101.site/2018/07/17/java8-CompleteableFuture/</id>
<published>2018-07-17T17:11:57.000Z</published>
<updated>2018-07-20T03:10:04.409Z</updated>
<content type="html"><![CDATA[<h1 id="CompletableFuture简介"><a href="#CompletableFuture简介" class="headerlink" title="CompletableFuture简介"></a>CompletableFuture简介</h1><p>java8中新增加了java.util.concurrent.CompletableFuture类，作用类似RxJava。</p><p>实际开发中，我们经常需要达成以下目的：</p><ul><li>将两个异步计算合并为一个——这两个异步计算之间相互独立，同时第二个又依赖于第一个的结果。</li><li>等待 Future 集合中的所有任务都完成。</li><li>仅等待 Future 集合中最快结束的任务完成（有可能因为它们试图通过不同的方式计算同一个值），并返回它的结果。</li><li>通过编程方式完成一个 Future 任务的执行（即以手工设定异步操作结果的方式）。</li><li>应对 Future 的完成事件（即当 Future 的完成事件发生时会收到通知，并能使用 Future 计算的结果进行下一步的操作，不只是简单地阻塞等待操作的结果）</li></ul><p>新的CompletableFuture将使得这些成为可能。</p><a id="more"></a><h2 id="工厂构建"><a href="#工厂构建" class="headerlink" title="工厂构建"></a>工厂构建</h2><ul><li><p>runAsync , supplyAsync</p><blockquote><p>静态方法，创建一个CompletableFuture，runAsync没有返回值，supplyAsync有返回值</p></blockquote></li><li><p>completedFuture</p><blockquote><p>静态方法，创建一个已经完成的CompletableFuture</p></blockquote></li></ul><h2 id="等待完成"><a href="#等待完成" class="headerlink" title="等待完成"></a>等待完成</h2><ul><li><p>get</p><blockquote><p>等待完成，并获取结果</p></blockquote></li><li><p>join</p><blockquote><p>将异步执行的线程join过来，跟get类似，等待完成，但是是不返回结果</p></blockquote></li></ul><h2 id="设置状态"><a href="#设置状态" class="headerlink" title="设置状态"></a>设置状态</h2><ul><li><p>complete,completeExceptionally</p><blockquote><p>设置CompletableFuture为完成，用指定的对象返回</p></blockquote></li><li><p>obtrudeValue,obtrudeException</p><blockquote><p>强制返回/抛异常</p></blockquote></li><li><p>cancel</p><blockquote><p>取消</p></blockquote></li></ul><h2 id="根据状态操作"><a href="#根据状态操作" class="headerlink" title="根据状态操作"></a>根据状态操作</h2><ul><li><p>whenComplete</p><blockquote><p>当本 CompletableFuture 执行完成后使用 BiConsumer 函数返回一个新的CompletableFuture， BiConsumer 第一个参数为返回值，第二个参数为异常</p></blockquote></li><li><p>handle</p><blockquote><p>当本CompletableFuture 执行完成后执行 BiConsumer 的函数，BiFunction第一个参数为返回值，第二个参数为异常，需要返回</p></blockquote></li><li><p>exceptionally</p><blockquote><p>当本CompletableFuture执行异常时，使用Function返回一个新的CompletableFuture</p></blockquote></li></ul><h2 id="状态判断"><a href="#状态判断" class="headerlink" title="状态判断"></a>状态判断</h2><ul><li>isDone,isCompletedExceptionally,isCancelled<blockquote><p>返回是否完成/异常/取消</p></blockquote></li></ul><h2 id="逻辑转换，单个"><a href="#逻辑转换，单个" class="headerlink" title="逻辑转换，单个"></a>逻辑转换，单个</h2><ul><li><p>thenApply,thenApplyAsync</p><blockquote><p>CompletableFuture正常结束后，使用Function函数应用一个新的CompletableFuture，Function函数有返回值</p></blockquote></li><li><p>thenAccept</p><blockquote><p>CompletableFuture正常结束后，使用Consumer函数应用一个新的CompletableFuture，Consumer函数没有返回值</p></blockquote></li><li><p>thenRun</p><blockquote><p>CompletableFuture正常结束后，使用Runnable函数应用一个新的CompletableFuture，Runnable函数没有输入值和返回值</p></blockquote></li></ul><h1 id="逻辑转换，两个"><a href="#逻辑转换，两个" class="headerlink" title="逻辑转换，两个"></a>逻辑转换，两个</h1><ul><li><p>thenAcceptBoth</p><blockquote><p>当本CompletableFuture和给定的CompletableFuture正常完成后，执行BiFunction函数并返回，BiFunction的输入参数为两个CompletableFuture的返回值</p></blockquote></li><li><p>thenCombine</p><blockquote><p>当本CompletableFuture和给定的CompletableFuture正常完成后，使用BiFunction函数生成一个新的CompletableFuture，BiFunction的输入参数为两个CompletableFuture的返回值。<br>两个CompletableFuture执行完后再执行指定函数</p></blockquote></li><li><p>thenCompose</p><blockquote><p>当本CompletableFuture完成后，将返回结果作为参数传递给Function函数，此Function函数返回一个新的CompletableFuture。<br>第一个CompletableFuture执行完后，结果传递给第二个CompletableFuture，返回第二个CompletableFuture</p></blockquote></li><li><p>applyToEither</p><blockquote><p>本 CompletableFuture 或者给定的CompletableFuture，任意一个做完后，使用Function生成一个新的CompletableFuture并返回</p></blockquote></li><li><p>acceptEither</p><blockquote><p>本 CompletableFuture 或者给定的CompletableFuture，任意一个做完后，使用Consumer生成一个新的CompletableFuture并返回</p></blockquote></li><li><p>runAfterEither</p><blockquote><p>本 CompletableFuture 或者给定的 CompletableFuture，任意一个做完后，使用Runnable生成一个新的CompletableFuture并返回</p></blockquote></li><li><p>runAfterBoth</p><blockquote><p>本CompletableFuture和给定的CompletableFuture，都完成后，使用Runnable生成一个新的CompletableFuture并返回</p></blockquote></li></ul><h2 id="逻辑转换，多个"><a href="#逻辑转换，多个" class="headerlink" title="逻辑转换，多个"></a>逻辑转换，多个</h2><ul><li><p>allOf</p><blockquote><p>静态方法，返回一个新的CompletableFuture，当所有的CompletableFuture都完成后才完成</p></blockquote></li><li><p>anyOf</p><blockquote><p>静态方法，返回一个新的CompletableFuture，任意一个CompletableFuture都完成后就完成</p></blockquote></li></ul><h1 id="demo"><a href="#demo" class="headerlink" title="demo"></a>demo</h1><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br><span class="line">117</span><br><span class="line">118</span><br><span class="line">119</span><br><span class="line">120</span><br><span class="line">121</span><br><span class="line">122</span><br><span class="line">123</span><br><span class="line">124</span><br><span class="line">125</span><br><span class="line">126</span><br><span class="line">127</span><br><span class="line">128</span><br><span class="line">129</span><br><span class="line">130</span><br><span class="line">131</span><br><span class="line">132</span><br><span class="line">133</span><br><span class="line">134</span><br><span class="line">135</span><br><span class="line">136</span><br><span class="line">137</span><br><span class="line">138</span><br><span class="line">139</span><br><span class="line">140</span><br><span class="line">141</span><br><span class="line">142</span><br><span class="line">143</span><br><span class="line">144</span><br><span class="line">145</span><br><span class="line">146</span><br><span class="line">147</span><br><span class="line">148</span><br><span class="line">149</span><br><span class="line">150</span><br><span class="line">151</span><br><span class="line">152</span><br><span class="line">153</span><br><span class="line">154</span><br><span class="line">155</span><br><span class="line">156</span><br><span class="line">157</span><br><span class="line">158</span><br><span class="line">159</span><br><span class="line">160</span><br><span class="line">161</span><br><span class="line">162</span><br><span class="line">163</span><br><span class="line">164</span><br><span class="line">165</span><br><span class="line">166</span><br><span class="line">167</span><br><span class="line">168</span><br><span class="line">169</span><br><span class="line">170</span><br><span class="line">171</span><br><span class="line">172</span><br><span class="line">173</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">CompletableFutureTest</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">sleep</span><span class="params">(<span class="keyword">int</span> s)</span> </span>{</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> TimeUnit.SECONDS.sleep(s);</span><br><span class="line"> } <span class="keyword">catch</span> (InterruptedException e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test1</span><span class="params">()</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> CompletableFuture<String> completableFuture = <span class="keyword">new</span> CompletableFuture<>();</span><br><span class="line"> <span class="keyword">new</span> Thread(() -> {</span><br><span class="line"> <span class="comment">//模拟执行耗时任务</span></span><br><span class="line"> System.out.println(<span class="string">"task doing..."</span>);</span><br><span class="line"> sleep(<span class="number">1</span>);</span><br><span class="line"> <span class="comment">//告诉completableFuture任务已经完成</span></span><br><span class="line"> completableFuture.complete(<span class="string">"result"</span>);</span><br><span class="line"> }).start();</span><br><span class="line"> <span class="comment">//获取任务结果，如果没有完成会一直阻塞等待</span></span><br><span class="line"> String result = completableFuture.get();</span><br><span class="line"> System.out.println(<span class="string">"计算结果:"</span> + result);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test2</span><span class="params">()</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> CompletableFuture<String> completableFuture = <span class="keyword">new</span> CompletableFuture<>();</span><br><span class="line"> <span class="keyword">new</span> Thread(() -> {</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//模拟执行耗时任务</span></span><br><span class="line"> System.out.println(<span class="string">"task doing..."</span>);</span><br><span class="line"> sleep(<span class="number">1</span>);</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> RuntimeException(<span class="string">"抛异常了"</span>);</span><br><span class="line"> } <span class="keyword">catch</span> (Exception e) {</span><br><span class="line"> <span class="comment">//告诉completableFuture任务发生异常了</span></span><br><span class="line"> completableFuture.completeExceptionally(e);</span><br><span class="line"> }</span><br><span class="line"> }).start();</span><br><span class="line"> <span class="comment">//获取任务结果，如果没有完成会一直阻塞等待</span></span><br><span class="line"> String result = completableFuture.get();</span><br><span class="line"> System.out.println(<span class="string">"计算结果:"</span> + result);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test3</span><span class="params">()</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> <span class="comment">//supplyAsync内部使用ForkJoinPool线程池执行任务</span></span><br><span class="line"> CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> {</span><br><span class="line"> <span class="comment">//模拟执行耗时任务</span></span><br><span class="line"> System.out.println(<span class="string">"task doing..."</span>);</span><br><span class="line"> sleep(<span class="number">1</span>);</span><br><span class="line"> <span class="comment">//返回结果</span></span><br><span class="line"> <span class="keyword">return</span> <span class="string">"result"</span>;</span><br><span class="line"> });</span><br><span class="line"> System.out.println(<span class="string">"计算结果:"</span> + completableFuture.get());</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> <span class="meta">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test4</span><span class="params">()</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> CompletableFuture<String> completableFuture1 = CompletableFuture.supplyAsync(() -> {</span><br><span class="line"> <span class="comment">//模拟执行耗时任务</span></span><br><span class="line"> System.out.println(<span class="string">"task1 doing..."</span>);</span><br><span class="line"> sleep(<span class="number">1</span>);</span><br><span class="line"> <span class="comment">//返回结果</span></span><br><span class="line"> <span class="keyword">return</span> <span class="string">"result1"</span>;</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> CompletableFuture<String> completableFuture2 = CompletableFuture.supplyAsync(() -> {</span><br><span class="line"> <span class="comment">//模拟执行耗时任务</span></span><br><span class="line"> System.out.println(<span class="string">"task2 doing..."</span>);</span><br><span class="line"> sleep(<span class="number">1</span>);</span><br><span class="line"> <span class="comment">//返回结果</span></span><br><span class="line"> <span class="keyword">return</span> <span class="string">"result2"</span>;</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> CompletableFuture<Object> anyResult = CompletableFuture.anyOf(completableFuture1, completableFuture2);</span><br><span class="line"> System.out.println(<span class="string">"第一个完成的任务结果:"</span> + anyResult.get());</span><br><span class="line"> CompletableFuture<Void> allResult = CompletableFuture.allOf(completableFuture1, completableFuture2);</span><br><span class="line"> <span class="comment">//阻塞等待所有任务执行完成</span></span><br><span class="line"> allResult.join();</span><br><span class="line"> System.out.println(<span class="string">"所有任务执行完成"</span>);</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test5</span><span class="params">()</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> CompletableFuture<String> completableFuture1 = CompletableFuture.supplyAsync(() -> {</span><br><span class="line"> <span class="comment">//模拟执行耗时任务</span></span><br><span class="line"> System.out.println(<span class="string">"task1 doing..."</span>);</span><br><span class="line"> sleep(<span class="number">1</span>);</span><br><span class="line"> <span class="comment">//返回结果</span></span><br><span class="line"> <span class="keyword">return</span> <span class="string">"result1"</span>;</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="comment">//等第一个任务完成后，将任务结果传给参数result，执行后面的任务并返回一个代表任务的completableFuture</span></span><br><span class="line"> CompletableFuture<String> completableFuture2 = completableFuture1.thenCompose(result -> CompletableFuture.supplyAsync(() -> {</span><br><span class="line"> <span class="comment">//模拟执行耗时任务</span></span><br><span class="line"> System.out.println(<span class="string">"task2 doing..."</span>);</span><br><span class="line"> sleep(<span class="number">1</span>);</span><br><span class="line"> <span class="comment">//返回结果</span></span><br><span class="line"> <span class="keyword">return</span> <span class="string">"result2"</span>;</span><br><span class="line"> }));</span><br><span class="line"></span><br><span class="line"> System.out.println(completableFuture2.get());</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test6</span><span class="params">()</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"></span><br><span class="line"> CompletableFuture<Integer> completableFuture1 = CompletableFuture.supplyAsync(() -> {</span><br><span class="line"> <span class="comment">//模拟执行耗时任务</span></span><br><span class="line"> System.out.println(<span class="string">"task1 doing..."</span>);</span><br><span class="line"> sleep(<span class="number">1</span>);</span><br><span class="line"> <span class="comment">//返回结果</span></span><br><span class="line"> <span class="keyword">return</span> <span class="number">100</span>;</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="comment">//将第一个任务与第二个任务组合一起执行，都执行完成后，将两个任务的结果合并</span></span><br><span class="line"> CompletableFuture<Integer> completableFuture2 = completableFuture1.thenCombine(</span><br><span class="line"> <span class="comment">//第二个任务</span></span><br><span class="line"> CompletableFuture.supplyAsync(() -> {</span><br><span class="line"> <span class="comment">//模拟执行耗时任务</span></span><br><span class="line"> System.out.println(<span class="string">"task2 doing..."</span>);</span><br><span class="line"> sleep(<span class="number">1</span>);</span><br><span class="line"> <span class="comment">//返回结果</span></span><br><span class="line"> <span class="keyword">return</span> <span class="number">2000</span>;</span><br><span class="line"> }),</span><br><span class="line"> <span class="comment">//合并函数</span></span><br><span class="line"> (result1, result2) -> result1 + result2);</span><br><span class="line"></span><br><span class="line"> System.out.println(completableFuture2.get());</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test7</span><span class="params">()</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"></span><br><span class="line"> CompletableFuture<Integer> completableFuture1 = CompletableFuture.supplyAsync(() -> {</span><br><span class="line"> <span class="comment">//模拟执行耗时任务</span></span><br><span class="line"> System.out.println(<span class="string">"task1 doing..."</span>);</span><br><span class="line"> sleep(<span class="number">1</span>);</span><br><span class="line"> <span class="comment">//返回结果</span></span><br><span class="line"> <span class="keyword">return</span> <span class="number">100</span>;</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="comment">//注册完成事件</span></span><br><span class="line"> completableFuture1.thenAccept(result -> System.out.println(<span class="string">"task1 done,result:"</span> + result));</span><br><span class="line"> <span class="comment">//第二个任务</span></span><br><span class="line"> CompletableFuture<Integer> completableFuture2 = CompletableFuture.supplyAsync(() -> {</span><br><span class="line"> <span class="comment">//模拟执行耗时任务</span></span><br><span class="line"> System.out.println(<span class="string">"task2 doing..."</span>);</span><br><span class="line"> sleep(<span class="number">1</span>);</span><br><span class="line"> <span class="comment">//返回结果</span></span><br><span class="line"> <span class="keyword">return</span> <span class="number">2000</span>;</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="comment">//注册完成事件</span></span><br><span class="line"> completableFuture2.thenAccept(result -> System.out.println(<span class="string">"task2 done,result:"</span> + result));</span><br><span class="line"></span><br><span class="line"> <span class="comment">//将第一个任务与第二个任务组合一起执行，都执行完成后，将两个任务的结果合并</span></span><br><span class="line"> CompletableFuture<Integer> completableFuture3 = completableFuture1.thenCombine(completableFuture2,</span><br><span class="line"> <span class="comment">//合并函数</span></span><br><span class="line"> (result1, result2) -> {</span><br><span class="line"> sleep(<span class="number">1</span>);</span><br><span class="line"> <span class="keyword">return</span> result1 + result2;</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> System.out.println(completableFuture3.get());</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<h1 id="CompletableFuture简介"><a href="#CompletableFuture简介" class="headerlink" title="CompletableFuture简介"></a>CompletableFuture简介</h1><p>java8中新增加了java.util.concurrent.CompletableFuture类，作用类似RxJava。</p>
<p>实际开发中，我们经常需要达成以下目的：</p>
<ul>
<li>将两个异步计算合并为一个——这两个异步计算之间相互独立，同时第二个又依赖于第一个的结果。</li>
<li>等待 Future 集合中的所有任务都完成。</li>
<li>仅等待 Future 集合中最快结束的任务完成（有可能因为它们试图通过不同的方式计算同一个值），并返回它的结果。</li>
<li>通过编程方式完成一个 Future 任务的执行（即以手工设定异步操作结果的方式）。</li>
<li>应对 Future 的完成事件（即当 Future 的完成事件发生时会收到通知，并能使用 Future 计算的结果进行下一步的操作，不只是简单地阻塞等待操作的结果）</li>
</ul>
<p>新的CompletableFuture将使得这些成为可能。</p>
</summary>
<category term="java" scheme="http://along101.site/categories/java/"/>
<category term="java8" scheme="http://along101.site/tags/java8/"/>
<category term="reactor" scheme="http://along101.site/tags/reactor/"/>
<category term="CompletableFuture" scheme="http://along101.site/tags/CompletableFuture/"/>
</entry>
<entry>
<title>java8 stream应用</title>
<link href="http://along101.site/2018/07/17/java8-stream/"/>
<id>http://along101.site/2018/07/17/java8-stream/</id>
<published>2018-07-17T17:05:57.000Z</published>
<updated>2018-07-20T03:10:04.409Z</updated>
<content type="html"><![CDATA[<h1 id="stream简介"><a href="#stream简介" class="headerlink" title="stream简介"></a>stream简介</h1><p>Java 8 中的 Stream 是对集合（Collection）对象功能的增强，它专注于对集合对象进行各种非常便利、高效的聚合操作（aggregate operation），或者大批量数据操作 (bulk data operation)。Stream API 借助于同样新出现的 Lambda 表达式，极大的提高编程效率和程序可读性。</p><a id="more"></a><h1 id="stream的生成"><a href="#stream的生成" class="headerlink" title="stream的生成"></a>stream的生成</h1><h3 id="从-Collection-和数组"><a href="#从-Collection-和数组" class="headerlink" title="从 Collection 和数组"></a>从 Collection 和数组</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">Collection.stream()</span><br><span class="line">Collection.parallelStream()</span><br><span class="line">Arrays.stream(T array) </span><br><span class="line">Stream.of()</span><br></pre></td></tr></table></figure><h3 id="从-BufferedReader"><a href="#从-BufferedReader" class="headerlink" title="从 BufferedReader"></a>从 BufferedReader</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">java.io.BufferedReader.lines()</span><br></pre></td></tr></table></figure><h3 id="静态工厂"><a href="#静态工厂" class="headerlink" title="静态工厂"></a>静态工厂</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">java.util.stream.IntStream.range()</span><br><span class="line">java.nio.file.Files.walk()</span><br></pre></td></tr></table></figure><h3 id="其它"><a href="#其它" class="headerlink" title="其它"></a>其它</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">Random.ints()</span><br><span class="line">BitSet.stream()</span><br><span class="line">Pattern.splitAsStream(java.lang.CharSequence)</span><br><span class="line">JarFile.stream()</span><br></pre></td></tr></table></figure><h3 id="Stream-generate"><a href="#Stream-generate" class="headerlink" title="Stream.generate"></a>Stream.generate</h3><ul><li>生成 10 个随机整数<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">Random seed = <span class="keyword">new</span> Random();</span><br><span class="line">Supplier<Integer> random = seed::nextInt;</span><br><span class="line">Stream.generate(random).limit(<span class="number">10</span>).forEach(System.out::println);</span><br><span class="line"><span class="comment">//Another way</span></span><br><span class="line">IntStream.generate(() -> (<span class="keyword">int</span>) (System.nanoTime() % <span class="number">100</span>)).</span><br><span class="line">limit(<span class="number">10</span>).forEach(System.out::println);</span><br></pre></td></tr></table></figure></li></ul><h3 id="Stream-iterate"><a href="#Stream-iterate" class="headerlink" title="Stream.iterate"></a>Stream.iterate</h3><p>iterate 跟 reduce 操作很像，接受一个种子值，和一个 UnaryOperator（例如 f）。然后种子值成为 Stream 的第一个元素，f(seed) 为第二个，f(f(seed)) 第三个，以此类推。</p><ul><li>生成一个等差数列<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">Stream.iterate(<span class="number">0</span>, n -> n + <span class="number">3</span>).limit(<span class="number">10</span>). forEach(x -> System.out.print(x + <span class="string">" "</span>));</span><br></pre></td></tr></table></figure></li></ul><h1 id="流的使用详解"><a href="#流的使用详解" class="headerlink" title="流的使用详解"></a>流的使用详解</h1><blockquote><p>简单说，对 Stream 的使用就是实现一个 filter-map-reduce 过程，产生一个最终结果，或者导致一个副作用</p></blockquote><p><strong>当把一个数据结构包装成Stream 后，就要开始对里面的元素进行各类操作了。常见的操作可以归类如下。</strong></p><ul><li>Intermediate：</li></ul><blockquote><p>map (mapToInt, flatMap 等)、 filter、 distinct、 sorted、 peek、 limit、 skip、 parallel、 sequential、 unordered</p></blockquote><ul><li>Terminal：</li></ul><blockquote><p>forEach、 forEachOrdered、 toArray、 reduce、 collect、 min、 max、 count、 anyMatch、 allMatch、 noneMatch、 findFirst、 findAny、 iterator</p></blockquote><ul><li>Short-circuiting：</li></ul><blockquote><p>anyMatch、 allMatch、 noneMatch、 findFirst、 findAny、 limit</p></blockquote><h3 id="map-flatMap"><a href="#map-flatMap" class="headerlink" title="map/flatMap"></a>map/flatMap</h3><p>作用就是把 input Stream 的每一个元素，映射成 output Stream 的另外一个元素。</p><ul><li><p>转换大写</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">List<String> output = wordList.stream().</span><br><span class="line">map(String::toUpperCase).</span><br><span class="line">collect(Collectors.toList());</span><br></pre></td></tr></table></figure></li><li><p>平方数</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">List<Integer> nums = Arrays.asList(<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>);</span><br><span class="line">List<Integer> squareNums = nums.stream().</span><br><span class="line">map(n -> n * n).</span><br><span class="line">collect(Collectors.toList());</span><br></pre></td></tr></table></figure></li><li><p>一对多</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">Stream<List<Integer>> inputStream = Stream.of(</span><br><span class="line"> Arrays.asList(<span class="number">1</span>),</span><br><span class="line"> Arrays.asList(<span class="number">2</span>, <span class="number">3</span>),</span><br><span class="line"> Arrays.asList(<span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>)</span><br><span class="line"> );</span><br><span class="line">Stream<Integer> outputStream = inputStream.</span><br><span class="line">flatMap((childList) -> childList.stream());</span><br></pre></td></tr></table></figure></li></ul><h3 id="filter"><a href="#filter" class="headerlink" title="filter"></a>filter</h3><p>filter 对原始 Stream 进行某项测试，通过测试的元素被留下来生成一个新 Stream。</p><ul><li><p>留下偶数</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">Integer[] sixNums = {<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>};</span><br><span class="line">Integer[] evens =</span><br><span class="line">Stream.of(sixNums).filter(n -> n%<span class="number">2</span> == <span class="number">0</span>).toArray(Integer[]::<span class="keyword">new</span>);</span><br></pre></td></tr></table></figure></li><li><p>把单词挑出来</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">List<String> output = reader.lines().</span><br><span class="line"> flatMap(line -> Stream.of(line.split(REGEXP))).</span><br><span class="line"> filter(word -> word.length() > <span class="number">0</span>).</span><br><span class="line"> collect(Collectors.toList());</span><br></pre></td></tr></table></figure></li></ul><h3 id="forEach"><a href="#forEach" class="headerlink" title="forEach"></a>forEach</h3><p>forEach 方法接收一个 Lambda 表达式，然后在 Stream 的每一个元素上执行该表达式。</p><ul><li>打印姓名（forEach 和 pre-java8 的对比）<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// Java 8</span></span><br><span class="line">roster.stream()</span><br><span class="line"> .filter(p -> p.getGender() == Person.Sex.MALE)</span><br><span class="line"> .forEach(p -> System.out.println(p.getName()));</span><br><span class="line"><span class="comment">// Pre-Java 8</span></span><br><span class="line"><span class="keyword">for</span> (Person p : roster) {</span><br><span class="line"> <span class="keyword">if</span> (p.getGender() == Person.Sex.MALE) {</span><br><span class="line"> System.out.println(p.getName());</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></li></ul><h3 id="findFirst"><a href="#findFirst" class="headerlink" title="findFirst"></a>findFirst</h3><p>这是一个 termimal 兼 short-circuiting 操作，它总是返回 Stream 的第一个元素，或者空。这里比较重点的是它的返回值类型：Optional。这也是一个模仿 Scala 语言中的概念，作为一个容器，它可能含有某值，或者不包含。使用它的目的是尽可能避免 NullPointerException。</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line">String strA = <span class="string">" abcd "</span>, strB = <span class="keyword">null</span>;</span><br><span class="line">print(strA);</span><br><span class="line">print(<span class="string">""</span>);</span><br><span class="line">print(strB);</span><br><span class="line">getLength(strA);</span><br><span class="line">getLength(<span class="string">""</span>);</span><br><span class="line">getLength(strB);</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">print</span><span class="params">(String text)</span> </span>{</span><br><span class="line"> <span class="comment">// Java 8</span></span><br><span class="line"> Optional.ofNullable(text).ifPresent(System.out::println);</span><br><span class="line"> <span class="comment">// Pre-Java 8</span></span><br><span class="line"> <span class="keyword">if</span> (text != <span class="keyword">null</span>) {</span><br><span class="line"> System.out.println(text);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">int</span> <span class="title">getLength</span><span class="params">(String text)</span> </span>{</span><br><span class="line"> <span class="comment">// Java 8</span></span><br><span class="line"><span class="keyword">return</span> Optional.ofNullable(text).map(String::length).orElse(-<span class="number">1</span>);</span><br><span class="line"> <span class="comment">// Pre-Java 8</span></span><br><span class="line"><span class="comment">// return if (text != null) ? text.length() : -1;</span></span><br><span class="line"> };</span><br></pre></td></tr></table></figure><blockquote><p>在更复杂的 if (xx != null) 的情况中，使用 Optional 代码的可读性更好，而且它提供的是编译时检查，能极大的降低 NPE 这种 Runtime Exception 对程序的影响，或者迫使程序员更早的在编码阶段处理空值问题，而不是留到运行时再发现和调试。Stream 中的 findAny、max/min、reduce 等方法等返回 Optional 值。还有例如 IntStream.average() 返回 OptionalDouble 等等。</p></blockquote><h3 id="reduce"><a href="#reduce" class="headerlink" title="reduce"></a>reduce</h3><blockquote><p>T reduce(T identity, BinaryOperator<t> accumulator) 这个方法的主要作用是把 Stream 元素组合起来。它提供一个起始值（种子），然后依照运算规则（BinaryOperator），和前面 Stream 的第一个、第二个、第 n 个元素组合。从这个意义上说，字符串拼接、数值的 sum、min、max、average 都是特殊的 reduce.也有没有起始值的情况，这时会把 Stream 的前面两个元素组合起来，返回的是 Optional。</t></p></blockquote><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 字符串连接，concat = "ABCD"</span></span><br><span class="line">String concat = Stream.of(<span class="string">"A"</span>, <span class="string">"B"</span>, <span class="string">"C"</span>, <span class="string">"D"</span>).reduce(<span class="string">""</span>, String::concat); </span><br><span class="line"><span class="comment">// 求最小值，minValue = -3.0</span></span><br><span class="line"><span class="keyword">double</span> minValue = Stream.of(-<span class="number">1.5</span>, <span class="number">1.0</span>, -<span class="number">3.0</span>, -<span class="number">2.0</span>).reduce(Double.MAX_VALUE, Double::min); </span><br><span class="line"><span class="comment">// 求和，sumValue = 10, 有起始值</span></span><br><span class="line"><span class="keyword">int</span> sumValue = Stream.of(<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>).reduce(<span class="number">0</span>, Integer::sum);</span><br><span class="line"><span class="comment">// 求和，sumValue = 10, 无起始值</span></span><br><span class="line">sumValue = Stream.of(<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>).reduce(Integer::sum).get();</span><br><span class="line"><span class="comment">// 过滤，字符串连接，concat = "ace"</span></span><br><span class="line">concat = Stream.of(<span class="string">"a"</span>, <span class="string">"B"</span>, <span class="string">"c"</span>, <span class="string">"D"</span>, <span class="string">"e"</span>, <span class="string">"F"</span>).</span><br><span class="line"> filter(x -> x.compareTo(<span class="string">"Z"</span>) > <span class="number">0</span>).</span><br><span class="line"> reduce(<span class="string">""</span>, String::concat);</span><br></pre></td></tr></table></figure><h3 id="limit-skip"><a href="#limit-skip" class="headerlink" title="limit/skip"></a>limit/skip</h3><blockquote><p>limit 返回 Stream 的前面 n 个元素；skip 则是扔掉前 n 个元素（它是由一个叫 subStream 的方法改名而来）。</p></blockquote><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">testLimitAndSkip</span><span class="params">()</span> </span>{</span><br><span class="line"> List<Person> persons = <span class="keyword">new</span> ArrayList();</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">1</span>; i <= <span class="number">10000</span>; i++) {</span><br><span class="line"> Person person = <span class="keyword">new</span> Person(i, <span class="string">"name"</span> + i);</span><br><span class="line"> persons.add(person);</span><br><span class="line"> }</span><br><span class="line">List<String> personList2 = persons.stream().</span><br><span class="line">map(Person::getName).limit(<span class="number">10</span>).skip(<span class="number">3</span>).collect(Collectors.toList());</span><br><span class="line"> System.out.println(personList2);</span><br><span class="line">}</span><br><span class="line"><span class="keyword">private</span> <span class="class"><span class="keyword">class</span> <span class="title">Person</span> </span>{</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">int</span> no;</span><br><span class="line"> <span class="keyword">private</span> String name;</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="title">Person</span> <span class="params">(<span class="keyword">int</span> no, String name)</span> </span>{</span><br><span class="line"> <span class="keyword">this</span>.no = no;</span><br><span class="line"> <span class="keyword">this</span>.name = name;</span><br><span class="line"> }</span><br><span class="line"> <span class="function"><span class="keyword">public</span> String <span class="title">getName</span><span class="params">()</span> </span>{</span><br><span class="line"> System.out.println(name);</span><br><span class="line"> <span class="keyword">return</span> name;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="sorted"><a href="#sorted" class="headerlink" title="sorted"></a>sorted</h3><blockquote><p>对 Stream 的排序通过 sorted 进行，它比数组的排序更强之处在于你可以首先对 Stream 进行各类 map、filter、limit、skip 甚至 distinct 来减少元素数量后，再排序，这能帮助程序明显缩短执行时间。</p></blockquote><ul><li>排序前进行 limit 和 skip<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">List<Person> persons = <span class="keyword">new</span> ArrayList();</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">1</span>; i <= <span class="number">5</span>; i++) {</span><br><span class="line"> Person person = <span class="keyword">new</span> Person(i, <span class="string">"name"</span> + i);</span><br><span class="line"> persons.add(person);</span><br><span class="line"> }</span><br><span class="line">List<Person> personList2 = persons.stream().limit(<span class="number">2</span>).sorted((p1, p2) -> p1.getName().compareTo(p2.getName())).collect(Collectors.toList());</span><br><span class="line">System.out.println(personList2);</span><br></pre></td></tr></table></figure></li></ul><h3 id="min-max-distinct"><a href="#min-max-distinct" class="headerlink" title="min/max/distinct"></a>min/max/distinct</h3><blockquote><p>min 和 max 的功能也可以通过对 Stream 元素先排序，再 findFirst 来实现，但前者的性能会更好，为 O(n)，而 sorted 的成本是 O(n log n)。同时它们作为特殊的 reduce 方法被独立出来也是因为求最大最小值是很常见的操作。</p></blockquote><ul><li><p>找出最长一行的长度</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">BufferedReader br = <span class="keyword">new</span> BufferedReader(<span class="keyword">new</span> FileReader(<span class="string">"c:\\SUService.log"</span>));</span><br><span class="line"><span class="keyword">int</span> longest = br.lines().</span><br><span class="line"> mapToInt(String::length).</span><br><span class="line"> max().</span><br><span class="line"> getAsInt();</span><br><span class="line">br.close();</span><br><span class="line">System.out.println(longest);</span><br></pre></td></tr></table></figure></li><li><p>找出全文的单词，转小写，并排序</p></li></ul><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">List<String> words = br.lines().</span><br><span class="line"> flatMap(line -> Stream.of(line.split(<span class="string">" "</span>))).</span><br><span class="line"> filter(word -> word.length() > <span class="number">0</span>).</span><br><span class="line"> map(String::toLowerCase).</span><br><span class="line"> distinct().</span><br><span class="line"> sorted().</span><br><span class="line"> collect(Collectors.toList());</span><br><span class="line">br.close();</span><br><span class="line">System.out.println(words);</span><br></pre></td></tr></table></figure><h3 id="Match"><a href="#Match" class="headerlink" title="Match"></a>Match</h3><p>Stream 有三个 match 方法，从语义上说：</p><pre><code>allMatch：Stream 中全部元素符合传入的 predicate，返回 trueanyMatch：Stream 中只要有一个元素符合传入的 predicate，返回 truenoneMatch：Stream 中没有一个元素符合传入的 predicate，返回 true</code></pre><blockquote><p>它们都不是要遍历全部元素才能返回结果。例如 allMatch 只要一个元素不满足条件，就 skip 剩下的所有元素，返回 false。</p></blockquote><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">List<Person> persons = <span class="keyword">new</span> ArrayList();</span><br><span class="line">persons.add(<span class="keyword">new</span> Person(<span class="number">1</span>, <span class="string">"name"</span> + <span class="number">1</span>, <span class="number">10</span>));</span><br><span class="line">persons.add(<span class="keyword">new</span> Person(<span class="number">2</span>, <span class="string">"name"</span> + <span class="number">2</span>, <span class="number">21</span>));</span><br><span class="line">persons.add(<span class="keyword">new</span> Person(<span class="number">3</span>, <span class="string">"name"</span> + <span class="number">3</span>, <span class="number">34</span>));</span><br><span class="line">persons.add(<span class="keyword">new</span> Person(<span class="number">4</span>, <span class="string">"name"</span> + <span class="number">4</span>, <span class="number">6</span>));</span><br><span class="line">persons.add(<span class="keyword">new</span> Person(<span class="number">5</span>, <span class="string">"name"</span> + <span class="number">5</span>, <span class="number">55</span>));</span><br><span class="line"><span class="keyword">boolean</span> isAllAdult = persons.stream().</span><br><span class="line"> allMatch(p -> p.getAge() > <span class="number">18</span>);</span><br><span class="line">System.out.println(<span class="string">"All are adult? "</span> + isAllAdult);</span><br><span class="line"><span class="keyword">boolean</span> isThereAnyChild = persons.stream().</span><br><span class="line"> anyMatch(p -> p.getAge() < <span class="number">12</span>);</span><br><span class="line">System.out.println(<span class="string">"Any child? "</span> + isThereAnyChild);</span><br></pre></td></tr></table></figure><h2 id="用-Collectors-来进行-reduction-操作"><a href="#用-Collectors-来进行-reduction-操作" class="headerlink" title="用 Collectors 来进行 reduction 操作"></a>用 Collectors 来进行 reduction 操作</h2><blockquote><p>java.util.stream.Collectors 类的主要作用就是辅助进行各类有用的 reduction 操作，例如转变输出为 Collection，把 Stream 元素进行归组。</p></blockquote><ul><li>收集新的List<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">List<Integer> list = Stream.of(<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>).filter(p -> p > <span class="number">2</span>).collect(Collectors.toList());</span><br></pre></td></tr></table></figure></li></ul><h3 id="groupingBy-partitioningBy"><a href="#groupingBy-partitioningBy" class="headerlink" title="groupingBy/partitioningBy"></a>groupingBy/partitioningBy</h3><ul><li>按照年龄归组<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">Map<Integer, List<Person>> personGroups = Stream.generate(<span class="keyword">new</span> PersonSupplier()).</span><br><span class="line"> limit(<span class="number">100</span>).</span><br><span class="line"> collect(Collectors.groupingBy(Person::getAge));</span><br><span class="line">Iterator it = personGroups.entrySet().iterator();</span><br><span class="line"><span class="keyword">while</span> (it.hasNext()) {</span><br><span class="line"> Map.Entry<Integer, List<Person>> persons = (Map.Entry) it.next();</span><br><span class="line"> System.out.println(<span class="string">"Age "</span> + persons.getKey() + <span class="string">" = "</span> + persons.getValue().size());</span><br><span class="line">}</span><br></pre></td></tr></table></figure></li></ul><h2 id="reduce-与-collect区别"><a href="#reduce-与-collect区别" class="headerlink" title="reduce 与 collect区别"></a>reduce 与 collect区别</h2><blockquote><p>Stream.reduce，常用的方法有average, sum, min, max, count，返回单个的结果值，并且reduce操作每处理一个元素总是创建一个新值<br>Stream.collection与stream.reduce方法不同，Stream.collect修改现存的值，而不是每处理一个元素，创建一个新值</p></blockquote><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">LambdaMapReduce</span> </span>{ </span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> List<User> users = Arrays.asList( </span><br><span class="line"> <span class="keyword">new</span> User(<span class="number">1</span>, <span class="string">"张三"</span>, <span class="number">12</span>,User.Sex.MALE), </span><br><span class="line"> <span class="keyword">new</span> User(<span class="number">2</span>, <span class="string">"李四"</span>, <span class="number">21</span>, User.Sex.FEMALE), </span><br><span class="line"> <span class="keyword">new</span> User(<span class="number">3</span>,<span class="string">"王五"</span>, <span class="number">32</span>, User.Sex.MALE), </span><br><span class="line"> <span class="keyword">new</span> User(<span class="number">4</span>, <span class="string">"赵六"</span>, <span class="number">32</span>, User.Sex.FEMALE)); </span><br><span class="line"> </span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>{ </span><br><span class="line"> reduceAvg(); </span><br><span class="line"> reduceSum(); </span><br><span class="line"> </span><br><span class="line"> </span><br><span class="line"> <span class="comment">//与stream.reduce方法不同，Stream.collect修改现存的值，而不是每处理一个元素，创建一个新值 </span></span><br><span class="line"> <span class="comment">//获取所有男性用户的平均年龄 </span></span><br><span class="line"> Averager averageCollect = users.parallelStream() </span><br><span class="line"> .filter(p -> p.getGender() == User.Sex.MALE) </span><br><span class="line"> .map(User::getAge) </span><br><span class="line"> .collect(Averager::<span class="keyword">new</span>, Averager::accept, Averager::combine); </span><br><span class="line"> </span><br><span class="line"> System.out.println(<span class="string">"Average age of male members: "</span> </span><br><span class="line"> + averageCollect.average()); </span><br><span class="line"> </span><br><span class="line"> <span class="comment">//获取年龄大于12的用户列表 </span></span><br><span class="line"> List<User> list = users.parallelStream().filter(p -> p.age > <span class="number">12</span>) </span><br><span class="line"> .collect(Collectors.toList()); </span><br><span class="line"> System.out.println(list); </span><br><span class="line"> </span><br><span class="line"> <span class="comment">//按性别统计用户数 </span></span><br><span class="line"> Map<User.Sex, Integer> map = users.parallelStream().collect( </span><br><span class="line"> Collectors.groupingBy(User::getGender, </span><br><span class="line"> Collectors.summingInt(p -> <span class="number">1</span>))); </span><br><span class="line"> System.out.println(map); </span><br><span class="line"> </span><br><span class="line"> <span class="comment">//按性别获取用户名称 </span></span><br><span class="line"> Map<User.Sex, List<String>> map2 = users.stream() </span><br><span class="line"> .collect( </span><br><span class="line"> Collectors.groupingBy( </span><br><span class="line"> User::getGender, </span><br><span class="line"> Collectors.mapping(User::getName, </span><br><span class="line"> Collectors.toList()))); </span><br><span class="line"> System.out.println(map2); </span><br><span class="line"> </span><br><span class="line"> <span class="comment">//按性别求年龄的总和 </span></span><br><span class="line"> Map<User.Sex, Integer> map3 = users.stream().collect( </span><br><span class="line"> Collectors.groupingBy(User::getGender, </span><br><span class="line"> Collectors.reducing(<span class="number">0</span>, User::getAge, Integer::sum))); </span><br><span class="line"> </span><br><span class="line"> System.out.println(map3); </span><br><span class="line"> </span><br><span class="line"> <span class="comment">//按性别求年龄的平均值 </span></span><br><span class="line"> Map<User.Sex, Double> map4 = users.stream().collect( </span><br><span class="line"> Collectors.groupingBy(User::getGender, </span><br><span class="line"> Collectors.averagingInt(User::getAge))); </span><br><span class="line"> System.out.println(map4); </span><br><span class="line"> </span><br><span class="line"> } </span><br><span class="line"> </span><br><span class="line"> <span class="comment">// 注意，reduce操作每处理一个元素总是创建一个新值， </span></span><br><span class="line"> <span class="comment">// Stream.reduce适用于返回单个结果值的情况 </span></span><br><span class="line"> <span class="comment">//获取所有用户的平均年龄 </span></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">reduceAvg</span><span class="params">()</span> </span>{ </span><br><span class="line"> <span class="comment">// mapToInt的pipeline后面可以是average,max,min,count,sum </span></span><br><span class="line"> <span class="keyword">double</span> avg = users.parallelStream().mapToInt(User::getAge) </span><br><span class="line"> .average().getAsDouble(); </span><br><span class="line"> </span><br><span class="line"> System.out.println(<span class="string">"reduceAvg User Age: "</span> + avg); </span><br><span class="line"> } </span><br><span class="line"> </span><br><span class="line"> <span class="comment">//获取所有用户的年龄总和 </span></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">reduceSum</span><span class="params">()</span> </span>{ </span><br><span class="line"> <span class="keyword">double</span> sum = users.parallelStream().mapToInt(User::getAge) </span><br><span class="line"> .reduce(<span class="number">0</span>, (x, y) -> x + y); <span class="comment">// 可以简写为.sum() </span></span><br><span class="line"> </span><br><span class="line"> System.out.println(<span class="string">"reduceSum User Age: "</span> + sum); </span><br><span class="line"> } </span><br><span class="line">}</span><br></pre></td></tr></table></figure><h1 id="参考"><a href="#参考" class="headerlink" title="参考"></a>参考</h1><p> <a href="https://github.com/along101/java-components-test/blob/master/java8/src/test/java/com/yzl/test/java8/stream/StreamTest.java" target="_blank" rel="noopener">github/along101</a></p>]]></content>
<summary type="html">
<h1 id="stream简介"><a href="#stream简介" class="headerlink" title="stream简介"></a>stream简介</h1><p>Java 8 中的 Stream 是对集合（Collection）对象功能的增强，它专注于对集合对象进行各种非常便利、高效的聚合操作（aggregate operation），或者大批量数据操作 (bulk data operation)。Stream API 借助于同样新出现的 Lambda 表达式，极大的提高编程效率和程序可读性。</p>
</summary>
<category term="java" scheme="http://along101.site/categories/java/"/>
<category term="java8" scheme="http://along101.site/tags/java8/"/>
<category term="stream" scheme="http://along101.site/tags/stream/"/>
</entry>
<entry>
<title>hexo博客使用Travis CI自动发布</title>
<link href="http://along101.site/2018/07/16/hexo-github-travis/"/>
<id>http://along101.site/2018/07/16/hexo-github-travis/</id>
<published>2018-07-16T11:09:13.000Z</published>
<updated>2018-07-20T03:10:04.405Z</updated>
<content type="html"><![CDATA[<h1 id="hexo-介绍"><a href="#hexo-介绍" class="headerlink" title="hexo 介绍"></a>hexo 介绍</h1><p>Hexo 是一个快速、简洁且高效的博客框架。Hexo 使用 Markdown（或其他渲染引擎）解析文章，在几秒内，即可利用靓丽的主题生成静态网页。</p><p>搭建hexo博客可以参考：<a href="http://techblog.ppdai.com/2018/07/06/20180706/" target="_blank" rel="noopener">http://techblog.ppdai.com/2018/07/06/20180706/</a></p><p><strong>本文主要介绍如何使用Travis CI自动发布blog，免除了在本地搭建nodejs、安装hexo和手工发布blog的繁琐过程。</strong></p><a id="more"></a><h1 id="思路"><a href="#思路" class="headerlink" title="思路"></a>思路</h1><p>hexo手工发布blog到github的原理是通过<code>hexo g</code>，将md文件生成静态的html文件，然后通过<code>hexo d</code>，将静态的html文件push到github仓库中。</p><p>这个过程都是在本地的nodejs环境中运行的，完全可以使用Travis来完成该过程。Travis是一个为GitHub服务的CI，可以把Travis看做一个远程服务器，它会监控你添加的GitHub库。如果有新的提交或Pull Request，就会触发一次在线编译，执行配置编译命令。</p><p>所以，可以将Hexo源码和blog静态页面放到github仓库的不同分支，在Hexo源码分支中添加Travis的配置，每当提交blog文档md后，Travis会自动生成静态页面并发push指定分支，完成blog的发布。</p><h1 id="hexo源码准备工作"><a href="#hexo源码准备工作" class="headerlink" title="hexo源码准备工作"></a>hexo源码准备工作</h1><ol><li><p>使用github搭建好个人blog</p><blockquote><p>参考<a href="http://techblog.ppdai.com/2018/07/06/20180706/" target="_blank" rel="noopener">http://techblog.ppdai.com/2018/07/06/20180706/</a></p></blockquote></li><li><p>创建分支存放hexo源码及blog源文件</p></li></ol><p>在username.github.io中创建分支可以命名问hexo，将hexo源代码已经blog源文件提交到该分支。master为blog生成后的html静态页面分支。</p><h1 id="Travis设置"><a href="#Travis设置" class="headerlink" title="Travis设置"></a>Travis设置</h1><p>1.进入官网<a href="https://www.travis-ci.org/" target="_blank" rel="noopener">https://www.travis-ci.org/</a>，使用github账号登录。<br>2.添加仓库<code>username.github.io</code></p><p><img src="/2018/07/16/hexo-github-travis/travis.png" alt="travis"></p><ol start="3"><li><p>在github添加Access Token，在travis中用此token push commit到github</p><p><img src="/2018/07/16/hexo-github-travis/github-token.png" alt="github-token"></p></li><li><p>在Travis设置页面将上一步生成的token添加到环境变量中，命名为myblog</p></li></ol><p><img src="/2018/07/16/hexo-github-travis/travis-token.png" alt="travis-token"></p><ol start="5"><li>在<code>username.github.io</code>仓库hexo分支中添加’.travis.yml’配置文件</li></ol><figure class="highlight yaml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line"><span class="attr">language:</span> <span class="string">node_js</span></span><br><span class="line"><span class="attr">node_js:</span> <span class="string">stable</span></span><br><span class="line"></span><br><span class="line"><span class="comment"># S: Build Lifecycle</span></span><br><span class="line"><span class="attr">install:</span></span><br><span class="line"><span class="bullet"> -</span> <span class="string">npm</span> <span class="string">install</span></span><br><span class="line"></span><br><span class="line"><span class="comment">#before_script:</span></span><br><span class="line"> <span class="comment"># - npm install -g gulp</span></span><br><span class="line"></span><br><span class="line"><span class="attr">script:</span></span><br><span class="line"><span class="bullet"> -</span> <span class="string">hexo</span> <span class="string">g</span></span><br><span class="line"></span><br><span class="line"><span class="attr">after_script:</span></span><br><span class="line"><span class="bullet"> -</span> <span class="string">cd</span> <span class="string">./public</span></span><br><span class="line"><span class="bullet"> -</span> <span class="string">git</span> <span class="string">init</span></span><br><span class="line"><span class="bullet"> -</span> <span class="string">git</span> <span class="string">config</span> <span class="string">user.name</span> <span class="string">"along101"</span></span><br><span class="line"><span class="bullet"> -</span> <span class="string">git</span> <span class="string">config</span> <span class="string">user.email</span> <span class="string">"[email protected]"</span></span><br><span class="line"><span class="bullet"> -</span> <span class="string">git</span> <span class="string">add</span> <span class="string">.</span></span><br><span class="line"><span class="bullet"> -</span> <span class="string">git</span> <span class="string">commit</span> <span class="bullet">-m</span> <span class="string">"Update docs"</span></span><br><span class="line"><span class="bullet"> -</span> <span class="string">git</span> <span class="string">push</span> <span class="bullet">--force</span> <span class="bullet">--quiet</span> <span class="string">"https://${myblog}@${GH_REF}"</span> <span class="attr">master:master</span></span><br><span class="line"></span><br><span class="line"><span class="comment"># E: Build LifeCycle</span></span><br><span class="line"><span class="attr">branches:</span></span><br><span class="line"><span class="attr"> only:</span></span><br><span class="line"><span class="bullet"> -</span> <span class="string">hexo</span></span><br><span class="line"><span class="attr">env:</span></span><br><span class="line"><span class="attr"> global:</span></span><br><span class="line"><span class="attr"> - GH_REF:</span> <span class="string">github.com/along101/along101.github.io.git</span></span><br></pre></td></tr></table></figure><p><code>${myblog}</code>为上一步添加的环境变量，需要配置自己的</p><ul><li><code>user.name</code> github用户名</li><li><code>user.email</code> github注册邮箱</li><li><code>GH_REF</code> 仓库地址</li></ul><ol start="6"><li>提交该配置到git仓库，Travis就会自动发布blog，以后写blog，只需要在hexo分支的<code>source/_posts</code>目录下提交blog的md文档，Travis就会自动发布静态页面到master上</li></ol><p><img src="/2018/07/16/hexo-github-travis/travis-build.png" alt="travis-build"></p>]]></content>
<summary type="html">
<h1 id="hexo-介绍"><a href="#hexo-介绍" class="headerlink" title="hexo 介绍"></a>hexo 介绍</h1><p>Hexo 是一个快速、简洁且高效的博客框架。Hexo 使用 Markdown（或其他渲染引擎）解析文章，在几秒内，即可利用靓丽的主题生成静态网页。</p>
<p>搭建hexo博客可以参考：<a href="http://techblog.ppdai.com/2018/07/06/20180706/" target="_blank" rel="noopener">http://techblog.ppdai.com/2018/07/06/20180706/</a></p>
<p><strong>本文主要介绍如何使用Travis CI自动发布blog，免除了在本地搭建nodejs、安装hexo和手工发布blog的繁琐过程。</strong></p>
</summary>
<category term="工具" scheme="http://along101.site/categories/%E5%B7%A5%E5%85%B7/"/>
<category term="hexo" scheme="http://along101.site/tags/hexo/"/>
<category term="blog" scheme="http://along101.site/tags/blog/"/>
<category term="travis" scheme="http://along101.site/tags/travis/"/>
<category term="ci" scheme="http://along101.site/tags/ci/"/>
</entry>
<entry>
<title>Hexo+Github搭建个人博客</title>
<link href="http://along101.site/2018/07/15/hexo/"/>
<id>http://along101.site/2018/07/15/hexo/</id>
<published>2018-07-15T11:29:57.000Z</published>
<updated>2018-07-20T03:10:04.405Z</updated>
<content type="html"><![CDATA[<p>本篇作者<code>李志明</code>，转至 <a href="http://techblog.ppdai.com/2018/07/06/20180706/" target="_blank" rel="noopener">http://techblog.ppdai.com/2018/07/06/20180706/</a></p><h2 id="前言"><a href="#前言" class="headerlink" title="前言"></a>前言</h2><p>作为程序猿，相信大家都有过这样一个想法，搭建属于自己的博客网站，在上面写写技术文章，记录生活点滴，坚持下去会发现这是一件很有成就感的事情。最近刚好在学习这部分内容，深入进去后发现里面坑很多，为了节省大家的时间，少走一点弯路，我整理出了这篇文章供大家参考。</p><a id="more"></a><h2 id="为什么选择Hexo"><a href="#为什么选择Hexo" class="headerlink" title="为什么选择Hexo"></a>为什么选择Hexo</h2><p>之前在网上搜了一下目前比较流行的静态博客框架，最后目标锁定在Jekyll和Hexo上，两者都支持Markdown语法，这点我很喜欢，Jekyll基于Ruby实现，安装Jekyll需要搭建Ruby环境，而Hexo基于NodeJs实现，在Windows上安装NodeJs开发环境比Ruby简单，另外Hexo的主题相对来说更符合我的审美，所以最终选择了Hexo。</p><p>什么是Hexo？官网对它的介绍是：</p><blockquote><p>Hexo 是一个快速、简洁且高效的博客框架。Hexo 使用 Markdown（或其他渲染引擎）解析文章，在几秒内，即可利用靓丽的主题生成静态网页。</p></blockquote><h2 id="准备工作"><a href="#准备工作" class="headerlink" title="准备工作"></a>准备工作</h2><h3 id="安装Node-js"><a href="#安装Node-js" class="headerlink" title="安装Node.js"></a>安装Node.js</h3><p>下载地址：<a href="https://nodejs.org/en/download/" target="_blank" rel="noopener">https://nodejs.org/en/download/</a></p><p>推荐下载LTS版本的msi文件，默认64-bit，也可根据自己的Windows版本选择32-bit。</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/nodejs-install/nodejs-download.png" alt=""></p><p>保持默认设置即可，一路Next。安装完成后打开命令行窗口，输入命令：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">$ node -v</span><br><span class="line">$ npm -v</span><br></pre></td></tr></table></figure><p>结果如下图所示，则说明安装正确，可以进行下一步，如果不正确，请回头检查自己的安装过程。</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/nodejs-install/nodejs6.png" alt=""></p><h3 id="安装git"><a href="#安装git" class="headerlink" title="安装git"></a>安装git</h3><p>下载地址：<a href="https://git-scm.com/downloads" target="_blank" rel="noopener">https://git-scm.com/downloads</a></p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/git-install/git-download.png" alt=""></p><p>保持默认设置即可，一路Next。安装完成后打开命令行窗口，输入：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ git --version</span><br></pre></td></tr></table></figure><p>结果如下图所示，则说明安装正确，可以进行下一步，如果不正确，请回头检查自己的安装过程。</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/git-install/git11.png" alt=""></p><h3 id="github配置"><a href="#github配置" class="headerlink" title="github配置"></a>github配置</h3><p>第一步，注册一个github账号，记得点击邮箱中的验证链接，注册地址：<a href="https://github.com" target="_blank" rel="noopener">https://github.com</a></p><p>第二步，生成SSH keys</p><p>什么是ssh：ssh是Secure Shell（安全外壳协议）的缩写，建立在应用层和传输层基础上的安全协议。为了便于访问github，要生成ssh公钥，这样就不用每一次访问github都要输入用户名和密码。</p><p>1.本地成功安装git后，单击鼠标右键，选择Git Bash Here，打开git bash。</p><p>2.输入命令：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ ssh-keygen -t rsa -C <span class="string">"[email protected]"</span></span><br></pre></td></tr></table></figure><p>引号中的内容是你在github上的注册邮箱，之后一路回车，结果如图所示：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/git-config/git-sshkey1.png" alt=""></p><p>3.上一步已经成功的生成了ssh key，接下来输入：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ <span class="built_in">eval</span> <span class="string">"ssh-agent -s"</span></span><br></pre></td></tr></table></figure><p>然后输入：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ ssh-add ~/.ssh/id_rsa</span><br></pre></td></tr></table></figure><p>这一步可能会报错：<code>Could not open a connection to your authentication agent</code> ，这时直接输入：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ ssh-agent bash</span><br></pre></td></tr></table></figure><p>再次输入：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ ssh-add ~/.ssh/id_rsa</span><br></pre></td></tr></table></figure><p>结果如图所示：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/git-config/git-sshkey2.png" alt=""></p><p>4.用cat命令查看key的内容：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ cat ~/.ssh/id_rsa.pub</span><br></pre></td></tr></table></figure><p>选中内容，右键复制备用，如图：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/git-config/git-sshkey3.png" alt=""></p><p>第三步，配置SSH keys</p><p>打开github页面，找到setting中的ssh keys，点击新增按钮，输入任意的title，将刚才复制的key粘贴进去保存即可。</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/git-config/git-config1.png" alt=""></p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/git-config/git-config2.png" alt=""></p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/git-config/git-config3.png" alt=""></p><p>第四步，测试</p><p>输入命令：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ ssh -T [email protected]</span><br></pre></td></tr></table></figure><p>结果如图：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/git-config/git-sshkey4.png" alt=""></p><p>到这里为止，准备工作就全部完成了。</p><h2 id="Hexo的安装与配置"><a href="#Hexo的安装与配置" class="headerlink" title="Hexo的安装与配置"></a>Hexo的安装与配置</h2><p>第一步，安装Hexo</p><p>打开命令行窗口，输入命令：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ npm install -g hexo-cli</span><br></pre></td></tr></table></figure><p>安装完成后输入：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo version</span><br></pre></td></tr></table></figure><p>结果如下图所示，则说明安装正确。</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo2.png" alt=""></p><p>如果报错：<code>'hexo'不是内部或外部命令，也不是可运行的程序或批处理文件</code> ，则需要检查环境变量配置是否正确，如下图所示，编辑Path变量值，在结尾处加上：<code>C:\Program Files\nodejs\node_global;</code>（文件hexo.cmd所在目录）</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/nodejs-install/nodejs7.png" alt=""></p><p>第二步，初始化Hexo</p><p>进入任意目录，比如F盘，然后指定一个文件夹名，这里以blog为例，命令如下：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo init blog</span><br></pre></td></tr></table></figure><p>结果如下图所示，F盘下会多出一个blog文件夹：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo3.png" alt=""></p><p>接下来进入blog目录：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ <span class="built_in">cd</span> blog</span><br></pre></td></tr></table></figure><p>第三步，安装必要的依赖</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ npm install</span><br></pre></td></tr></table></figure><p>第四步，生成静态文件</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo generate</span><br></pre></td></tr></table></figure><p>该命令的简写形式为：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo g</span><br></pre></td></tr></table></figure><p>执行完毕后会在blog目录下生成一个public文件夹，里面包含了博客网站的所有静态资源。</p><p>第五步，启动服务器</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo server</span><br></pre></td></tr></table></figure><p>该命令的简写形式为：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo s</span><br></pre></td></tr></table></figure><p>默认情况下，访问地址为：<a href="http://localhost:4000/" target="_blank" rel="noopener">http://localhost:4000/</a></p><p>另外也可以指定端口（比如8000）：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo s -p 8000</span><br></pre></td></tr></table></figure><p>第六步，验证</p><p>在浏览器中打开上面的地址，你将会看到：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo1.png" alt=""></p><p>到这里为止，Hexo的安装与相关配置就全部完成了。</p><h2 id="将Hexo与Github-Pages联系起来"><a href="#将Hexo与Github-Pages联系起来" class="headerlink" title="将Hexo与Github Pages联系起来"></a>将Hexo与Github Pages联系起来</h2><p>第一步，创建代码库</p><p>1.登录github，点击页面右上角的加号，选择New repository</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/git-config/git-config4.png" alt=""></p><p>2.在Repository name中填写 <code>yourname.github.io</code> ，注意这里的yourname指的是你的github用户名，如果你的名字是kirito，那就填 <code>kirito.github.io</code> ，Description中可以填一些简单的描述，不写也没关系，然后点击Create repository</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/git-config/git-config5.png" alt=""></p><p>3.正确创建之后，你会看到如下界面：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/git-config/git-config6.png" alt=""></p><p>第二步，编辑站点配置文件</p><p>打开blog目录下的_config.yml文件，编辑deploy模块，内容如下：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">deploy:</span><br><span class="line"> type: git</span><br><span class="line"> repo: [email protected]:lizhiming1995/yourname.github.io.git</span><br><span class="line"> branch: master</span><br></pre></td></tr></table></figure><p>注意这里的repo地址应该换成你第一步创建的代码库的地址。</p><p>第三步，安装一个扩展</p><p>进入blog目录，打开命令行窗口，输入命令：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ npm install hexo-deployer-git --save</span><br></pre></td></tr></table></figure><p>安装完成后，就可以一键部署到github上了。</p><p>第四步，部署</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo deploy</span><br></pre></td></tr></table></figure><p>该命令的简写形式为：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo d</span><br></pre></td></tr></table></figure><p>执行结果如图所示：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo4.png" alt=""></p><p>这样你public目录下的静态文件就上传到你的代码库中了。</p><p>第五步，激活GitHub Pages</p><p>打开代码库的Settings页面，找到GitHub Pages，选择master branch，然后点击Save按钮，如图：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo5.png" alt=""></p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo6.png" alt=""></p><p>最后会提示你：<code>Your site is ready to be published at http://yourname.github.io/</code></p><p>这就是你的博客地址了，任何人都可以访问哦。</p><h2 id="绑定自己的域名"><a href="#绑定自己的域名" class="headerlink" title="绑定自己的域名"></a>绑定自己的域名</h2><p>第一步，在万网、腾讯云、阿里云等提供域名注册的域名服务商处购买一个域名，这里以阿里云为例，购买地址：<a href="https://wanwang.aliyun.com/" target="_blank" rel="noopener">https://wanwang.aliyun.com/</a></p><p>第二步，打开控制台，给域名添加DNS解析</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/dns1.png" alt=""></p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/dns2.png" alt=""></p><p>添加两条解析记录，记录类型为CNAME，主机记录分别填@和www，记录值填之前GitHub Pages提供的域名，注意没有http的前缀，如下图：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/dns3.png" alt=""></p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/dns4.png" alt=""></p><p>添加完后别人用www和不用www都能访问你的网站。</p><p>第三步，在blog目录的source文件夹下创建一个CNAME文件，记住不要有文件后缀名，编辑CNAME文件，里面写你购买的域名，例如 <code>yourname.com</code> ，记住不要有www，创建完成后每一次执行 <code>hexo g</code> 都会在public文件夹下生成CNAME文件，方便后面的部署</p><p>第四步，在blog目录下打开命令行窗口，运行 <code>hexo g</code> ，再运行 <code>hexo d</code></p><p>第五步，在浏览器输入你购买的域名，你会发现该域名已经指向了你在github上的博客地址</p><p>注意：设置域名解析需要几分钟的时间，若完成以上步骤依然无法访问，请过几分钟再尝试</p><h2 id="Hexo入门"><a href="#Hexo入门" class="headerlink" title="Hexo入门"></a>Hexo入门</h2><p>我们先来看一下blog的目录结构：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">+ blog</span><br><span class="line"> + public //静态资源文件夹，内容会推送到代码库</span><br><span class="line"> + scaffolds //模板文件夹，新建文章时，Hexo会根据模板来建立文件</span><br><span class="line"> + source //资源文件夹，Markdown和HTML文件会被解析并放到public文件夹，而其他文件会被拷贝过去</span><br><span class="line"> + themes //主题文件夹，Hexo会根据主题来生成静态页面</span><br><span class="line"> - _config.yml //网站的配置信息，可以在此配置大部分的参数</span><br><span class="line"> - package.json //应用程序的信息和依赖关系</span><br></pre></td></tr></table></figure><p>方便起见，我们把网站的语言设置为中文，编辑blog目录下的_config.yml文件，将language这一项设置为 <code>language: zh-CN</code>（参考blog/themes/landscape/languages目录），将url这一项设置为 <code>url: http://yourname.com</code>（你购买的域名，若未购买可以用 <code>http://yourname.github.io</code> 代替），其他配置项请根据自己的需要进行设置。</p><p>接下来新建一篇文章：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo new [layout] <title></span><br></pre></td></tr></table></figure><p>layout可选值有：draft（草稿）、page（页面）、post（文章），对应模板文件夹中的3个文件，如果没有设置layout的话，默认使用_config.yml中的default_layout参数（默认值post）代替。若标题包含空格，请使用引号括起来。</p><p>现在，我们来新建一篇名为test的文章，输入以下命令：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo new <span class="built_in">test</span></span><br></pre></td></tr></table></figure><p>结果在source/_posts目录下生成了test.md文件，内容如下：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">---</span><br><span class="line">title: test</span><br><span class="line">date: 2018-06-23 19:14:56</span><br><span class="line">tags:</span><br><span class="line">---</span><br></pre></td></tr></table></figure><p>这里给出Front-matter的概念，Front-matter是文件最上方以 <code>---</code> 分隔的区域，用于指定文件的变量。</p><p>常见参数：title（标题）、date（创建日期）、tags（标签）、categories（分类），只有文章（post）支持标签和分类参数，建议文章分类只写一个，标签可以有多个，写法为 <code>tags: [tag1,tag2,tag3]</code> ，注意每个参数的冒号后面都应该有一个空格，这一点同样体现在_config.yml文件中</p><p>编辑test.md文件，内容如下：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">---</span><br><span class="line">title: test</span><br><span class="line">date: 2018-06-23 19:14:56</span><br><span class="line">tags: [tag1,tag2,tag3]</span><br><span class="line">categories: java</span><br><span class="line">---</span><br><span class="line">文章正文</span><br></pre></td></tr></table></figure><p>保存后刷新页面，通常情况下页面会自动更新，若修改没有生效，则需要重新执行以下命令：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">$ hexo g</span><br><span class="line">$ hexo s</span><br></pre></td></tr></table></figure><p>这里再介绍一个命令：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo clean</span><br></pre></td></tr></table></figure><p>它的作用是清除缓存文件 (db.json) 和已生成的静态文件 (public)。在某些情况下（尤其是更换主题后），如果你发现对站点的更改无论如何也不生效，你可能需要运行该命令。</p><p>打开网站首页，你会看到刚才设置的标签和分类生效了：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo7.png" alt=""></p><p>发现Hello World这篇文章的内容被折叠起来了吗，很简单，只需要在文章正文合适的地方加上 <code><!--more--></code> 这一行代码就搞定了。</p><p>菜单栏只有Home和Archives？没关系，我们可以加个页面（page），这里以about为例，在blog目录下打开命令行窗口，输入命令：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo new page about</span><br></pre></td></tr></table></figure><p>结果会在source目录下生成about文件夹，里面包含一个index.md文件，文件内容就是about页面的内容。</p><p>还没有结束，编辑blog/themes/landscape目录下的_config.yml文件，修改menu的配置为：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">menu:</span><br><span class="line"> 首页: /</span><br><span class="line"> 归档: /archives</span><br><span class="line"> 关于: /about</span><br></pre></td></tr></table></figure><p>保存刷新页面，你会看到导航栏里多了“关于”，点进去就是about页面啦，目前只有一个标题，内容待编辑，注意页面是不支持设置标签和分类的，只有文章才支持。</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo8.png" alt=""></p><p>最后，我们来总结一下发布文章的流程：</p><p>第一步，<code>hexo new <title></code> 生成一篇文章，这里的title指文件名，不建议使用中文</p><p>第二步，编辑文章，修改title、tags等参数，这里的title指文章标题，可以使用中文</p><p>第三步，<code>hexo s</code> 本地预览效果，不满意继续修改</p><p>第四步，<code>hexo g</code> 生成静态文件</p><p>第五步，<code>hexo d</code> 将静态文件推送至代码库</p><p>第四步和第五步可以合并成一条命令，<code>hexo d -g</code> ，表示部署之前预先生成静态文件。修改配置与发布文章的流程相似，最后都需要执行第三四五步。</p><h2 id="Hexo进阶"><a href="#Hexo进阶" class="headerlink" title="Hexo进阶"></a>Hexo进阶</h2><h3 id="添加RSS订阅功能"><a href="#添加RSS订阅功能" class="headerlink" title="添加RSS订阅功能"></a>添加RSS订阅功能</h3><p>RSS是在线共享内容的一种简易方式，也叫简易信息聚合，全称Really Simple Syndication。当网站内容更新时，可以通过订阅RSS源在RSS阅读器上获取更新的信息，大多数的内容提供网站都会提供RSS订阅功能，方便用户去获取最新的内容。</p><p>1.安装feed插件</p><p>Hexo有一个专门生成RSS文件的插件 <code>hexo-generator-feed</code> ，进入blog目录，打开命令行窗口，输入命令：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ npm install hexo-generator-feed --save</span><br></pre></td></tr></table></figure><p>2.启用插件</p><p>编辑blog目录下的_config.yml文件，添加如下内容：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"># Extensions</span><br><span class="line">Plugins:</span><br><span class="line">- hexo-generator-feed</span><br><span class="line"># Feed Atom</span><br><span class="line">feed:</span><br><span class="line"> type: atom</span><br><span class="line"> path: atom.xml</span><br><span class="line"> limit: 20</span><br></pre></td></tr></table></figure><p>3.生成RSS</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo g</span><br></pre></td></tr></table></figure><p>如果生成了atom.xml就表示成功了：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo9.png" alt=""></p><p>在浏览器中打开 <a href="http://localhost:4000/atom.xml" target="_blank" rel="noopener">http://localhost:4000/atom.xml</a> ，你会看到订阅功能已开启：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo10.png" alt=""></p><p>4.部署</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo d</span><br></pre></td></tr></table></figure><p>5.使用RSS订阅功能</p><p>这里以Office的Outlook邮箱为例，订阅地址假设为 <code>http://spring2go.com/atom.xml</code>，如图：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo11.png" alt=""></p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo12.png" alt=""></p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo13.png" alt=""></p><h3 id="添加站点地图"><a href="#添加站点地图" class="headerlink" title="添加站点地图"></a>添加站点地图</h3><p>站点地图是一种文件，你可以通过该文件列出你网站上的网页，从而将你网站内容的组织架构告知Google和其他搜索引擎。Googlebot等搜索引擎网页抓取工具会读取此文件，以便更加智能地抓取你的网站。</p><p>1.安装sitemap插件</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">$ npm install hexo-generator-sitemap --save</span><br><span class="line">$ npm install hexo-generator-baidu-sitemap --save</span><br></pre></td></tr></table></figure><p>2.编辑blog目录下的_config.yml文件，添加如下内容：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">Plugins:</span><br><span class="line">- hexo-generator-sitemap</span><br><span class="line">- hexo-generator-baidu-sitemap</span><br><span class="line"></span><br><span class="line">sitemap:</span><br><span class="line"> path: sitemap.xml</span><br><span class="line"></span><br><span class="line">baidusitemap:</span><br><span class="line"> path: baidusitemap.xml</span><br></pre></td></tr></table></figure><p>3.生成站点地图文件</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo g</span><br></pre></td></tr></table></figure><p>如果生成了sitemap.xml和baidusitemap.xml就表示成功了：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo15.png" alt=""></p><p>4.部署</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo d</span><br></pre></td></tr></table></figure><p>5.确认博客是否被收录</p><p>在百度或者谷歌输入下面格式的内容，如果能搜索到就说明被收录，否则未收录，可能需要等上一段时间。</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">site:xxx.com</span><br></pre></td></tr></table></figure><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo14.png" alt=""></p><h3 id="使用模板功能"><a href="#使用模板功能" class="headerlink" title="使用模板功能"></a>使用模板功能</h3><p>现在我们生成的每一篇新文章都只有title、date、tags三个参数，通常情况下我们还会有categories参数和一些自定义的参数（如何使用自定义参数我们后面讲），每次都要手动加上这些参数会浪费很多时间，这时候模板的作用就出来了。</p><p>打开scaffolds文件夹，你会看到里面有draft、page、post三个模板，对应草稿、页面、文章，我们日常使用最多的就是文章，所以这里以文章为例，其他两个模板请根据自己的需要进行修改。</p><p>模板的参数是可以设置默认值的，我们假设categories参数的默认值为 <code>随笔</code> ，然后自定义一个参数 <code>author</code> ，默认值为 <code>kirito</code> ，因为每篇文章的标签是不确定的，所以这里不进行设置，编辑post.md文件，内容如下：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">---</span><br><span class="line">title: {{ title }}</span><br><span class="line">date: {{ date }}</span><br><span class="line">tags: </span><br><span class="line">categories: 随笔</span><br><span class="line">author: kirito</span><br><span class="line">---</span><br></pre></td></tr></table></figure><p>让我们用模板生成一篇新文章：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo new test2</span><br></pre></td></tr></table></figure><p>打开blog/source/_posts目录下的test2.md文件，可以看到以下内容：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">---</span><br><span class="line">title: test2</span><br><span class="line">categories: 随笔</span><br><span class="line">author: kirito</span><br><span class="line">date: 2018-06-27 22:02:33</span><br><span class="line">tags:</span><br><span class="line">---</span><br></pre></td></tr></table></figure><p>接下来我们只需要写好文章，设置一下tags就可以发布了。</p><h3 id="使用自定义参数"><a href="#使用自定义参数" class="headerlink" title="使用自定义参数"></a>使用自定义参数</h3><p>文章参数里的title、date、categories和tags都在页面上有所展示，那我们自定义的参数该如何使用和展示呢？</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo16.png" alt=""></p><p>通过控制台我们可以看到，每篇文章都是一个 <code>class="article article-type-post"</code> 的 <code>article</code> 标签，结构如下：</p><figure class="highlight html"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">article</span> <span class="attr">id</span>=<span class="string">"post-test"</span> <span class="attr">class</span>=<span class="string">"article article-type-post"</span> <span class="attr">itemscope</span>=<span class="string">""</span> <span class="attr">itemprop</span>=<span class="string">"blogPost"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">div</span> <span class="attr">class</span>=<span class="string">"article-meta"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">a</span> <span class="attr">href</span>=<span class="string">"/2018/06/23/test/"</span> <span class="attr">class</span>=<span class="string">"article-date"</span>></span>...<span class="tag"></<span class="name">a</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">div</span> <span class="attr">class</span>=<span class="string">"article-category"</span>></span>...<span class="tag"></<span class="name">div</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">div</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">div</span> <span class="attr">class</span>=<span class="string">"article-inner"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">header</span> <span class="attr">class</span>=<span class="string">"article-header"</span>></span>...<span class="tag"></<span class="name">header</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">div</span> <span class="attr">class</span>=<span class="string">"article-entry"</span> <span class="attr">itemprop</span>=<span class="string">"articleBody"</span>></span>...<span class="tag"></<span class="name">div</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">footer</span> <span class="attr">class</span>=<span class="string">"article-footer"</span>></span>...<span class="tag"></<span class="name">footer</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">div</span>></span></span><br><span class="line"><span class="tag"></<span class="name">article</span>></span></span><br></pre></td></tr></table></figure><p>title、date、categories和tags的值分别显示于article-header、article-date、article-category和article-footer，要使用自定义参数，我们需要修改主题的源文件，打开 <code>blog/themes/landscape/layout/_partial</code> 目录下的article.ejs文件，可以看到代码中的标签与class名都与上面一致，接下来我们让作者的名字显示在分类右边，编辑article-meta模块的代码：</p><figure class="highlight html"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">div</span> <span class="attr">class</span>=<span class="string">"article-meta"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">%-</span> <span class="attr">partial</span>('<span class="attr">post</span>/<span class="attr">date</span>', {<span class="attr">class_name:</span> '<span class="attr">article-date</span>', <span class="attr">date_format:</span> <span class="attr">null</span>}) %></span></span><br><span class="line"> <span class="tag"><<span class="name">%-</span> <span class="attr">partial</span>('<span class="attr">post</span>/<span class="attr">category</span>') %></span></span><br><span class="line"> <span class="tag"><<span class="name">div</span> <span class="attr">style</span>=<span class="string">"letter-spacing:2px;color:#999;line-height:1em;"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">%-</span> <span class="attr">post.author</span> %></span></span><br><span class="line"> <span class="tag"></<span class="name">div</span>></span></span><br><span class="line"><span class="tag"></<span class="name">div</span>></span></span><br></pre></td></tr></table></figure><p>这里为了方便直接将样式写在了div标签里，更好的做法是为div添加一个class，将样式写进 <code>landscape/source/css/_partial</code><br> 目录下的article.styl文件。当然，自定义标签可以用在其他地方，样式也可以根据你的喜好来定制。</p><p>让我们打开浏览器来看下效果，你会发现文章的自定义标签生效了：</p><p><img src="https://images-1256966106.cos.ap-shanghai.myqcloud.com/hexo/hexo17.png" alt=""></p><p>值得注意的是，我们刚才修改的文件是article.ejs，这是跟主题有关的，换一个主题，也许文件的路径和名字都变了，甚至格式也不再是ejs而是swig，不过修改文件的思路都是一样的，明确自己要修改哪一个模块，然后到主题的相关目录下，模仿源代码的语法进行修改，最后记住，源文件里使用Tab键会导致修改的代码无效或者报错，请使用空格。</p><p>那么教程到这里就结束了，快来试试搭建自己的博客吧，有什么问题可以在评论区留言~</p><p>ps：后面我会单独整理一篇关于Hexo主题的文章，不用期待…</p>]]></content>
<summary type="html">
<p>本篇作者<code>李志明</code>，转至 <a href="http://techblog.ppdai.com/2018/07/06/20180706/" target="_blank" rel="noopener">http://techblog.ppdai.com/2018/07/06/20180706/</a></p>
<h2 id="前言"><a href="#前言" class="headerlink" title="前言"></a>前言</h2><p>作为程序猿，相信大家都有过这样一个想法，搭建属于自己的博客网站，在上面写写技术文章，记录生活点滴，坚持下去会发现这是一件很有成就感的事情。最近刚好在学习这部分内容，深入进去后发现里面坑很多，为了节省大家的时间，少走一点弯路，我整理出了这篇文章供大家参考。</p>
</summary>
<category term="工具" scheme="http://along101.site/categories/%E5%B7%A5%E5%85%B7/"/>
<category term="Hexo" scheme="http://along101.site/tags/Hexo/"/>
<category term="Github" scheme="http://along101.site/tags/Github/"/>
<category term="博客" scheme="http://along101.site/tags/%E5%8D%9A%E5%AE%A2/"/>
</entry>
<entry>
<title>spring-cloud-openfeign 深度分析</title>
<link href="http://along101.site/2018/06/15/spring-cloud-openfeign/"/>
<id>http://along101.site/2018/06/15/spring-cloud-openfeign/</id>
<published>2018-06-15T12:03:13.000Z</published>
<updated>2018-07-20T03:10:04.413Z</updated>
<content type="html"><![CDATA[<h1 id="简介"><a href="#简介" class="headerlink" title="简介"></a>简介</h1><p><a href="https://github.com/OpenFeign/feign" target="_blank" rel="noopener">feign</a>是一个声明试的HTTP客户端，spring-cloud-openfeign将feign集成到spring boot中，在接口上通过注解声明Rest协议，将http调用转换为接口方法的调用，使得客户端调用http服务更加简单。</p><p>当前spring cloud最新稳定版本是Edgware，feign在其集成的<a href="https://github.com/spring-cloud/spring-cloud-netflix" target="_blank" rel="noopener">spring-cloud-netflix</a> 1.4.0.RELEASE版本中。</p><blockquote><p>spring cloud下一个版本是Finchley，将会单独集成<a href="https://github.com/spring-cloud/spring-cloud-openfeign" target="_blank" rel="noopener">spring-cloud-openfeign</a></p></blockquote><a id="more"></a><h1 id="demo"><a href="#demo" class="headerlink" title="demo"></a>demo</h1><p>我们来看个简单的例子。源代码链接：<a href="https://github.com/along101/spring-boot-test/tree/master/feign-test" target="_blank" rel="noopener">https://github.com/along101/spring-boot-test/tree/master/feign-test</a></p><h2 id="服务端代码"><a href="#服务端代码" class="headerlink" title="服务端代码"></a>服务端代码</h2><p>使用spring boot编写一个简单的Rest服务<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RestController</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">HelloController</span> <span class="keyword">implements</span> <span class="title">HelloService</span> </span>{</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> String <span class="title">hello</span><span class="params">(@RequestParam(<span class="string">"name"</span>)</span> String name) </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="string">"Hello "</span> + name;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>接口代码：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping</span>(<span class="string">"/test"</span>)</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">HelloService</span> </span>{</span><br><span class="line"> <span class="meta">@RequestMapping</span>(value = <span class="string">"/hello1"</span>, method = RequestMethod.GET)</span><br><span class="line"> <span class="function">String <span class="title">hello</span><span class="params">(@RequestParam(<span class="string">"name"</span>)</span> String name)</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>代码很简单，通过springMVC注解在接口HelloService上声明Rest服务，HelloController被@RestController注解声明为一个Rest服务。</p><p>启动spring boot 就可通过浏览器访问<a href="http://localhost:8080/test/hello1?name=ppdai得到返回Hello" target="_blank" rel="noopener">http://localhost:8080/test/hello1?name=ppdai得到返回Hello</a> ppdai。</p><h2 id="客户端代码"><a href="#客户端代码" class="headerlink" title="客户端代码"></a>客户端代码</h2><p>客户端pom中需要加入spring-cloud-starter-feign的依赖<br><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">dependencies</span>></span></span><br><span class="line"> ...</span><br><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"><span class="tag"><<span class="name">groupId</span>></span>org.springframework.cloud<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"><span class="tag"><<span class="name">artifactId</span>></span>spring-cloud-starter-feign<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependency</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependencies</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="tag"><<span class="name">dependencyManagement</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">dependencies</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>org.springframework.cloud<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>spring-cloud-dependencies<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>Camden.SR7<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">type</span>></span>pom<span class="tag"></<span class="name">type</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">scope</span>></span>import<span class="tag"></<span class="name">scope</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">dependencies</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">dependencyManagement</span>></span></span><br></pre></td></tr></table></figure></p><p>在客户端中新建一个HelloClient接口继承服务端HelloService接口：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//在spring boot配置文件中配置remote.hello.service.host=http://localhost:8080</span></span><br><span class="line"><span class="meta">@FeignClient</span>(value = <span class="string">"HELLO-SERVICE"</span>, url = <span class="string">"${remote.hello.service.host}"</span>)</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">HelloClient</span> <span class="keyword">extends</span> <span class="title">HelloService</span> </span>{</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>HelloClient接口上注解@FeignClient，声明为Feign的客户端，参数url指定服务端地址。<br>在spring boot启动类上增加注解@EnableFeignClients</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@SpringBootApplication</span></span><br><span class="line"><span class="meta">@EnableFeignClients</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">FeignClientApplication</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>{</span><br><span class="line"> SpringApplication.run(FeignClientApplication.class, args);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>注意，HelloClient接口需要在启动类package或者子package之下。<br>编写测试类测试：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RunWith</span>(SpringJUnit4ClassRunner.class)</span><br><span class="line"><span class="meta">@SpringBootTest</span>(classes = FeignClientApplication.class)</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">HelloClientTest</span> </span>{</span><br><span class="line"> <span class="meta">@Autowired</span></span><br><span class="line"> <span class="keyword">private</span> HelloClient helloClient;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">testClient</span><span class="params">()</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> String result = helloClient.hello(<span class="string">"ppdai"</span>);</span><br><span class="line"> System.out.println(result);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>启动服务端后，运行该测试类，在控制台会打印出<code>Hello ppdai</code></p><h1 id="原理分析"><a href="#原理分析" class="headerlink" title="原理分析"></a>原理分析</h1><p>看到客户端测试类中，我们只用了一行代码，就能完成对远程Rest服务的调用，相当的简单。为什么这么神奇，这几段代码是如何做到的呢？</p><h2 id="EnableFeignClients-注解声明客户端接口"><a href="#EnableFeignClients-注解声明客户端接口" class="headerlink" title="@EnableFeignClients 注解声明客户端接口"></a>@EnableFeignClients 注解声明客户端接口</h2><p>入口是启动类上的注解@EnableFeignClients，源代码：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Retention</span>(RetentionPolicy.RUNTIME)</span><br><span class="line"><span class="meta">@Target</span>(ElementType.TYPE)</span><br><span class="line"><span class="meta">@Documented</span></span><br><span class="line"><span class="meta">@Import</span>(FeignClientsRegistrar.class)</span><br><span class="line"><span class="keyword">public</span> <span class="meta">@interface</span> EnableFeignClients {</span><br><span class="line"><span class="comment">//basePackages的别名</span></span><br><span class="line">String[] value() <span class="keyword">default</span> {};</span><br><span class="line"><span class="comment">//声明基础包，spring boot启动后，会扫描该包下被@FeignClient注解的接口</span></span><br><span class="line">String[] basePackages() <span class="keyword">default</span> {};</span><br><span class="line"><span class="comment">//声明基础包的类，通过该类声明基础包</span></span><br><span class="line">Class<?>[] basePackageClasses() <span class="keyword">default</span> {};</span><br><span class="line"><span class="comment">//默认配置类</span></span><br><span class="line">Class<?>[] defaultConfiguration() <span class="keyword">default</span> {};</span><br><span class="line"><span class="comment">//直接声明的客户端接口类</span></span><br><span class="line">Class<?>[] clients() <span class="keyword">default</span> {};</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>@EnableFeignClients的参数声明客户端接口的位置和默认的配置类。</p><h3 id="FeignClient注解，将接口声明为Feign客户端"><a href="#FeignClient注解，将接口声明为Feign客户端" class="headerlink" title="@FeignClient注解，将接口声明为Feign客户端"></a>@FeignClient注解，将接口声明为Feign客户端</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Target</span>(ElementType.TYPE)</span><br><span class="line"><span class="meta">@Retention</span>(RetentionPolicy.RUNTIME)</span><br><span class="line"><span class="meta">@Documented</span></span><br><span class="line"><span class="keyword">public</span> <span class="meta">@interface</span> FeignClient {</span><br><span class="line"></span><br><span class="line"><span class="meta">@AliasFor</span>(<span class="string">"name"</span>)</span><br><span class="line"><span class="function">String <span class="title">value</span><span class="params">()</span> <span class="keyword">default</span> ""</span>;</span><br><span class="line"><span class="comment">//名称，对应与eureka上注册的应用名</span></span><br><span class="line"><span class="meta">@AliasFor</span>(<span class="string">"value"</span>)</span><br><span class="line"><span class="function">String <span class="title">name</span><span class="params">()</span> <span class="keyword">default</span> ""</span>;</span><br><span class="line"><span class="comment">//生成spring bean的qualifier</span></span><br><span class="line"><span class="function">String <span class="title">qualifier</span><span class="params">()</span> <span class="keyword">default</span> ""</span>;</span><br><span class="line"><span class="comment">//http服务的url</span></span><br><span class="line"><span class="function">String <span class="title">url</span><span class="params">()</span> <span class="keyword">default</span> ""</span>;</span><br><span class="line"><span class="function"><span class="keyword">boolean</span> <span class="title">decode404</span><span class="params">()</span> <span class="keyword">default</span> <span class="keyword">false</span></span>;</span><br><span class="line"><span class="comment">//配置类，这里设置的配置类是Spring Configuration，将会在FeignContext中创建内部声明的Bean，用于不同的客户端进行隔离</span></span><br><span class="line">Class<?>[] configuration() <span class="keyword">default</span> {};</span><br><span class="line"><span class="comment">//声明hystrix调用失败后的方法</span></span><br><span class="line">Class<?> fallback() <span class="keyword">default</span> <span class="keyword">void</span>.class;</span><br><span class="line">Class<?> fallbackFactory() <span class="keyword">default</span> <span class="keyword">void</span>.class;</span><br><span class="line"><span class="function">String <span class="title">path</span><span class="params">()</span> <span class="keyword">default</span> ""</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h2 id="FeignClientsRegistrar-注册客户端"><a href="#FeignClientsRegistrar-注册客户端" class="headerlink" title="FeignClientsRegistrar 注册客户端"></a>FeignClientsRegistrar 注册客户端</h2><p>@EnableFeignClients注解上被注解了@Import(FeignClientsRegistrar.class)，@Import注解的作用是将指定的类作为Bean注入到Spring Context中，我们再来看被引入的FeignClientsRegistrar</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">FeignClientsRegistrar</span> <span class="keyword">implements</span> <span class="title">ImportBeanDefinitionRegistrar</span>,</span></span><br><span class="line"><span class="class"><span class="title">ResourceLoaderAware</span>, <span class="title">BeanClassLoaderAware</span> </span>{</span><br><span class="line">。。。</span><br><span class="line"></span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">registerBeanDefinitions</span><span class="params">(AnnotationMetadata metadata,</span></span></span><br><span class="line"><span class="function"><span class="params">BeanDefinitionRegistry registry)</span> </span>{</span><br><span class="line">registerDefaultConfiguration(metadata, registry);</span><br><span class="line">registerFeignClients(metadata, registry);</span><br><span class="line">}</span><br><span class="line">。。。</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>FeignClientsRegistrar类实现了3个接口:</p><ul><li>接口ResourceLoaderAware用于注入ResourceLoader</li><li>接口BeanClassLoaderAware用于注入ClassLoader</li><li>接口ImportBeanDefinitionRegistrar用于动态向Spring Context中注册bean</li></ul><p>ImportBeanDefinitionRegistrar接口方法registerBeanDefinitions有两个参数</p><ul><li>AnnotationMetadata 包含被@Import注解类的信息</li></ul><blockquote><p>这里 @Import注解在@EnableFeignClients上，@EnableFeignClients注解在spring boot启动类上，AnnotationMetadata拿到的是spring boot启动类的相关信息</p></blockquote><ul><li>BeanDefinitionRegistry bean定义注册中心</li></ul><h2 id="registerDefaultConfiguration方法，注册默认配置"><a href="#registerDefaultConfiguration方法，注册默认配置" class="headerlink" title="registerDefaultConfiguration方法，注册默认配置"></a>registerDefaultConfiguration方法，注册默认配置</h2><p>registerDefaultConfiguration方法代码：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title">registerDefaultConfiguration</span><span class="params">(AnnotationMetadata metadata,</span></span></span><br><span class="line"><span class="function"><span class="params">BeanDefinitionRegistry registry)</span> </span>{</span><br><span class="line"><span class="comment">//获取@EnableFeignClients注解参数</span></span><br><span class="line">Map<String, Object> defaultAttrs = metadata</span><br><span class="line">.getAnnotationAttributes(EnableFeignClients.class.getName(), <span class="keyword">true</span>);</span><br><span class="line"><span class="comment">//如果参数中包含defaultConfiguration</span></span><br><span class="line"><span class="keyword">if</span> (defaultAttrs != <span class="keyword">null</span> && defaultAttrs.containsKey(<span class="string">"defaultConfiguration"</span>)) {</span><br><span class="line">String name;</span><br><span class="line"><span class="keyword">if</span> (metadata.hasEnclosingClass()) {</span><br><span class="line">name = <span class="string">"default."</span> + metadata.getEnclosingClassName();</span><br><span class="line">}</span><br><span class="line"><span class="keyword">else</span> {</span><br><span class="line">name = <span class="string">"default."</span> + metadata.getClassName();</span><br><span class="line">}</span><br><span class="line"><span class="comment">//注册客户端的配置Bean</span></span><br><span class="line">registerClientConfiguration(registry, name,</span><br><span class="line">defaultAttrs.get(<span class="string">"defaultConfiguration"</span>));</span><br><span class="line">}</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>取出@EnableFeignClients注解参数defaultConfiguration，注册到spring Context中。registerClientConfiguration方法代码如下：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title">registerClientConfiguration</span><span class="params">(BeanDefinitionRegistry registry, Object name,</span></span></span><br><span class="line"><span class="function"><span class="params">Object configuration)</span> </span>{</span><br><span class="line"><span class="comment">// 创建一个BeanDefinitionBuilder，注册bean的类为FeignClientSpecification</span></span><br><span class="line">BeanDefinitionBuilder builder = BeanDefinitionBuilder</span><br><span class="line">.genericBeanDefinition(FeignClientSpecification.class);</span><br><span class="line"><span class="comment">//增加构造函数参数</span></span><br><span class="line">builder.addConstructorArgValue(name);</span><br><span class="line">builder.addConstructorArgValue(configuration);</span><br><span class="line"><span class="comment">//调用BeanDefinitionRegistry.registerBeanDefinition方法动态注册Bean</span></span><br><span class="line">registry.registerBeanDefinition(</span><br><span class="line">name + <span class="string">"."</span> + FeignClientSpecification.class.getSimpleName(),</span><br><span class="line">builder.getBeanDefinition());</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>这里使用spring 动态注册bean的方式，注册了一个FeignClientSpecification的bean。</p><h2 id="FeignClientSpecification-客户端定义"><a href="#FeignClientSpecification-客户端定义" class="headerlink" title="FeignClientSpecification 客户端定义"></a>FeignClientSpecification 客户端定义</h2><p>一个简单的pojo，继承了NamedContextFactory.Specification，两个属性String name 和 Class<?>[] configuration，用于FeignContext命名空间独立配置，后面会用到。</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Data</span></span><br><span class="line"><span class="meta">@AllArgsConstructor</span></span><br><span class="line"><span class="meta">@NoArgsConstructor</span></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">FeignClientSpecification</span> <span class="keyword">implements</span> <span class="title">NamedContextFactory</span>.<span class="title">Specification</span> </span>{</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> String name;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> Class<?>[] configuration;</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure><h2 id="registerFeignClients方法，注册feign客户端"><a href="#registerFeignClients方法，注册feign客户端" class="headerlink" title="registerFeignClients方法，注册feign客户端"></a>registerFeignClients方法，注册feign客户端</h2><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">registerFeignClients</span><span class="params">(AnnotationMetadata metadata,</span></span></span><br><span class="line"><span class="function"><span class="params">BeanDefinitionRegistry registry)</span> </span>{</span><br><span class="line"><span class="comment">//生成一个scanner，扫描注定包下的类</span></span><br><span class="line">ClassPathScanningCandidateComponentProvider scanner = getScanner();</span><br><span class="line">scanner.setResourceLoader(<span class="keyword">this</span>.resourceLoader);</span><br><span class="line"></span><br><span class="line">Set<String> basePackages;</span><br><span class="line"></span><br><span class="line">Map<String, Object> attrs = metadata</span><br><span class="line">.getAnnotationAttributes(EnableFeignClients.class.getName());</span><br><span class="line"><span class="comment">//包含@FeignClient注解的过滤器</span></span><br><span class="line">AnnotationTypeFilter annotationTypeFilter = <span class="keyword">new</span> AnnotationTypeFilter(</span><br><span class="line">FeignClient.class);</span><br><span class="line"><span class="keyword">final</span> Class<?>[] clients = attrs == <span class="keyword">null</span> ? <span class="keyword">null</span></span><br><span class="line">: (Class<?>[]) attrs.get(<span class="string">"clients"</span>);</span><br><span class="line"><span class="keyword">if</span> (clients == <span class="keyword">null</span> || clients.length == <span class="number">0</span>) {</span><br><span class="line"><span class="comment">//@EnableFeignClients没有声明clients，获取basePackages，设置过滤器</span></span><br><span class="line">scanner.addIncludeFilter(annotationTypeFilter);</span><br><span class="line">basePackages = getBasePackages(metadata);</span><br><span class="line">}</span><br><span class="line"><span class="keyword">else</span> {</span><br><span class="line"><span class="comment">//@EnableFeignClients声明了clients</span></span><br><span class="line"><span class="keyword">final</span> Set<String> clientClasses = <span class="keyword">new</span> HashSet<>();</span><br><span class="line">basePackages = <span class="keyword">new</span> HashSet<>();</span><br><span class="line"><span class="comment">//basePackages为声明的clients所在的包</span></span><br><span class="line"><span class="keyword">for</span> (Class<?> clazz : clients) {</span><br><span class="line">basePackages.add(ClassUtils.getPackageName(clazz));</span><br><span class="line">clientClasses.add(clazz.getCanonicalName());</span><br><span class="line">}</span><br><span class="line"><span class="comment">//增加过滤器，只包含声明的clients</span></span><br><span class="line">AbstractClassTestingTypeFilter filter = <span class="keyword">new</span> AbstractClassTestingTypeFilter() {</span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">protected</span> <span class="keyword">boolean</span> <span class="title">match</span><span class="params">(ClassMetadata metadata)</span> </span>{</span><br><span class="line">String cleaned = metadata.getClassName().replaceAll(<span class="string">"\\$"</span>, <span class="string">"."</span>);</span><br><span class="line"><span class="keyword">return</span> clientClasses.contains(cleaned);</span><br><span class="line">}</span><br><span class="line">};</span><br><span class="line">scanner.addIncludeFilter(</span><br><span class="line"><span class="keyword">new</span> AllTypeFilter(Arrays.asList(filter, annotationTypeFilter)));</span><br><span class="line">}</span><br><span class="line"><span class="comment">//遍历basePackages</span></span><br><span class="line"><span class="keyword">for</span> (String basePackage : basePackages) {</span><br><span class="line"><span class="comment">//扫描包，根据过滤器找到候选的Bean</span></span><br><span class="line">Set<BeanDefinition> candidateComponents = scanner</span><br><span class="line">.findCandidateComponents(basePackage);</span><br><span class="line"><span class="comment">// 遍历候选的bean</span></span><br><span class="line"><span class="keyword">for</span> (BeanDefinition candidateComponent : candidateComponents) {</span><br><span class="line"><span class="keyword">if</span> (candidateComponent <span class="keyword">instanceof</span> AnnotatedBeanDefinition) {</span><br><span class="line"><span class="comment">// 校验注解是否是注解在接口上</span></span><br><span class="line">AnnotatedBeanDefinition beanDefinition = (AnnotatedBeanDefinition) candidateComponent;</span><br><span class="line">AnnotationMetadata annotationMetadata = beanDefinition.getMetadata();</span><br><span class="line">Assert.isTrue(annotationMetadata.isInterface(),</span><br><span class="line"><span class="string">"@FeignClient can only be specified on an interface"</span>);</span><br><span class="line"><span class="comment">// 获取注解属性</span></span><br><span class="line">Map<String, Object> attributes = annotationMetadata</span><br><span class="line">.getAnnotationAttributes(</span><br><span class="line">FeignClient.class.getCanonicalName());</span><br><span class="line"></span><br><span class="line">String name = getClientName(attributes);</span><br><span class="line"><span class="comment">//注册客户端配置</span></span><br><span class="line">registerClientConfiguration(registry, name,</span><br><span class="line">attributes.get(<span class="string">"configuration"</span>));</span><br><span class="line"><span class="comment">//注册客户端</span></span><br><span class="line">registerFeignClient(registry, annotationMetadata, attributes);</span><br><span class="line">}</span><br><span class="line">}</span><br><span class="line">}</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>这个方法主要逻辑是扫描注解声明的客户端，调用registerFeignClient方法注册到registry中。这里是一个典型的spring动态注册bean的例子，可以参考这段代码在spring中轻松的实现类路径下class扫描，动态注册bean到spring中。想了解spring类的扫描机制，可以断点到ClassPathScanningCandidateComponentProvider.findCandidateComponents方法中，一步步调试。</p><h2 id="registerFeignClient方法，注册单个客户feign端"><a href="#registerFeignClient方法，注册单个客户feign端" class="headerlink" title="registerFeignClient方法，注册单个客户feign端"></a>registerFeignClient方法，注册单个客户feign端</h2><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title">registerFeignClient</span><span class="params">(BeanDefinitionRegistry registry,</span></span></span><br><span class="line"><span class="function"><span class="params">AnnotationMetadata annotationMetadata, Map<String, Object> attributes)</span> </span>{</span><br><span class="line">String className = annotationMetadata.getClassName();</span><br><span class="line"><span class="comment">//构建一个FeignClientFactoryBean的bean工厂定义</span></span><br><span class="line">BeanDefinitionBuilder definition = BeanDefinitionBuilder</span><br><span class="line">.genericBeanDefinition(FeignClientFactoryBean.class);</span><br><span class="line">validate(attributes);</span><br><span class="line"><span class="comment">//根据@FeignClient注解的参数，设置属性</span></span><br><span class="line">definition.addPropertyValue(<span class="string">"url"</span>, getUrl(attributes));</span><br><span class="line">definition.addPropertyValue(<span class="string">"path"</span>, getPath(attributes));</span><br><span class="line">String name = getName(attributes);</span><br><span class="line">definition.addPropertyValue(<span class="string">"name"</span>, name);</span><br><span class="line">definition.addPropertyValue(<span class="string">"type"</span>, className);</span><br><span class="line">definition.addPropertyValue(<span class="string">"decode404"</span>, attributes.get(<span class="string">"decode404"</span>));</span><br><span class="line">definition.addPropertyValue(<span class="string">"fallback"</span>, attributes.get(<span class="string">"fallback"</span>));</span><br><span class="line">definition.addPropertyValue(<span class="string">"fallbackFactory"</span>, attributes.get(<span class="string">"fallbackFactory"</span>));</span><br><span class="line">definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);</span><br><span class="line"></span><br><span class="line">String alias = name + <span class="string">"FeignClient"</span>;</span><br><span class="line">AbstractBeanDefinition beanDefinition = definition.getBeanDefinition();</span><br><span class="line">beanDefinition.setPrimary(<span class="keyword">true</span>);</span><br><span class="line"><span class="comment">//设置qualifier</span></span><br><span class="line">String qualifier = getQualifier(attributes);</span><br><span class="line"><span class="keyword">if</span> (StringUtils.hasText(qualifier)) {</span><br><span class="line">alias = qualifier;</span><br><span class="line">}</span><br><span class="line"><span class="comment">//注册，这里为了简写，新建一个BeanDefinitionHolder，调用BeanDefinitionReaderUtils静态方法注册</span></span><br><span class="line">BeanDefinitionHolder holder = <span class="keyword">new</span> BeanDefinitionHolder(beanDefinition, className,</span><br><span class="line"><span class="keyword">new</span> String[] { alias });</span><br><span class="line">BeanDefinitionReaderUtils.registerBeanDefinition(holder, registry);</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>registerFeignClient方法主要是将FeignClientFactoryBean工厂Bean注册到registry中，spring初始化后，会调用FeignClientFactoryBean的getObject方法创建bean注册到spring context中。</p><h2 id="FeignClientFactoryBean-创建feign客户端的工厂"><a href="#FeignClientFactoryBean-创建feign客户端的工厂" class="headerlink" title="FeignClientFactoryBean 创建feign客户端的工厂"></a>FeignClientFactoryBean 创建feign客户端的工厂</h2><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Data</span></span><br><span class="line"><span class="meta">@EqualsAndHashCode</span>(callSuper = <span class="keyword">false</span>)</span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">FeignClientFactoryBean</span> <span class="keyword">implements</span> <span class="title">FactoryBean</span><<span class="title">Object</span>>, <span class="title">InitializingBean</span>,</span></span><br><span class="line"><span class="class"><span class="title">ApplicationContextAware</span> </span>{</span><br><span class="line"><span class="comment">//feign客户端接口类</span></span><br><span class="line"><span class="keyword">private</span> Class<?> type;</span><br><span class="line"><span class="keyword">private</span> String name; </span><br><span class="line"><span class="keyword">private</span> String url;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> String path;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">boolean</span> decode404;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> ApplicationContext applicationContext;</span><br><span class="line"><span class="comment">//hystrix集成，调用失败的执行方法</span></span><br><span class="line"><span class="keyword">private</span> Class<?> fallback = <span class="keyword">void</span>.class;</span><br><span class="line"><span class="comment">//同上</span></span><br><span class="line"><span class="keyword">private</span> Class<?> fallbackFactory = <span class="keyword">void</span>.class;</span><br><span class="line">。。。</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>FeignClientFactoryBean实现了FactoryBean接口，是一个工厂bean</p><h3 id="FeignClientFactoryBean-getObject方法"><a href="#FeignClientFactoryBean-getObject方法" class="headerlink" title="FeignClientFactoryBean.getObject方法"></a>FeignClientFactoryBean.getObject方法</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> Object <span class="title">getObject</span><span class="params">()</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"><span class="comment">//FeignContext在FeignAutoConfiguration中自动注册，FeignContext用于客户端配置类独立注册，后面具体分析</span></span><br><span class="line">FeignContext context = applicationContext.getBean(FeignContext.class);</span><br><span class="line"><span class="comment">//创建Feign.Builder</span></span><br><span class="line">Feign.Builder builder = feign(context);</span><br><span class="line"><span class="comment">//如果@FeignClient注解没有设置url参数</span></span><br><span class="line"><span class="keyword">if</span> (!StringUtils.hasText(<span class="keyword">this</span>.url)) {</span><br><span class="line">String url;</span><br><span class="line"><span class="comment">//url为@FeignClient注解的name参数</span></span><br><span class="line"><span class="keyword">if</span> (!<span class="keyword">this</span>.name.startsWith(<span class="string">"http"</span>)) {</span><br><span class="line">url = <span class="string">"http://"</span> + <span class="keyword">this</span>.name;</span><br><span class="line">}</span><br><span class="line"><span class="keyword">else</span> {</span><br><span class="line">url = <span class="keyword">this</span>.name;</span><br><span class="line">}</span><br><span class="line"><span class="comment">//加上path</span></span><br><span class="line">url += cleanPath();</span><br><span class="line"><span class="comment">//返回loadBlance客户端，也就是ribbon+eureka的客户端</span></span><br><span class="line"><span class="keyword">return</span> loadBalance(builder, context, <span class="keyword">new</span> HardCodedTarget<>(<span class="keyword">this</span>.type,</span><br><span class="line"><span class="keyword">this</span>.name, url));</span><br><span class="line">}</span><br><span class="line"><span class="comment">//@FeignClient设置了url参数，不做负载均衡</span></span><br><span class="line"><span class="keyword">if</span> (StringUtils.hasText(<span class="keyword">this</span>.url) && !<span class="keyword">this</span>.url.startsWith(<span class="string">"http"</span>)) {</span><br><span class="line"><span class="keyword">this</span>.url = <span class="string">"http://"</span> + <span class="keyword">this</span>.url;</span><br><span class="line">}</span><br><span class="line"><span class="comment">//加上path</span></span><br><span class="line">String url = <span class="keyword">this</span>.url + cleanPath();</span><br><span class="line"><span class="comment">//从FeignContext中获取client</span></span><br><span class="line">Client client = getOptional(context, Client.class);</span><br><span class="line"><span class="keyword">if</span> (client != <span class="keyword">null</span>) {</span><br><span class="line"><span class="keyword">if</span> (client <span class="keyword">instanceof</span> LoadBalancerFeignClient) {</span><br><span class="line"><span class="comment">// 有url参数，不做负载均衡，但是客户端是ribbon，或者实际的客户端</span></span><br><span class="line">client = ((LoadBalancerFeignClient)client).getDelegate();</span><br><span class="line">}</span><br><span class="line">builder.client(client);</span><br><span class="line">}</span><br><span class="line"><span class="comment">//从FeignContext中获取Targeter</span></span><br><span class="line">Targeter targeter = get(context, Targeter.class);</span><br><span class="line"><span class="comment">//生成客户端代理</span></span><br><span class="line"><span class="keyword">return</span> targeter.target(<span class="keyword">this</span>, builder, context, <span class="keyword">new</span> HardCodedTarget<>(</span><br><span class="line"><span class="keyword">this</span>.type, <span class="keyword">this</span>.name, url));</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>这段代码有个比较重要的逻辑，如果在@FeignClient注解中设置了url参数，就不走Ribbon，直接url调用，否则通过Ribbon调用，实现客户端负载均衡。</p><p>可以看到，生成Feign客户端所需要的各种配置对象，都是通过FeignContex中获取的。</p><h3 id="FeignContext-隔离配置"><a href="#FeignContext-隔离配置" class="headerlink" title="FeignContext 隔离配置"></a>FeignContext 隔离配置</h3><p>在@FeignClient注解参数configuration，指定的类是Spring的Configuration Bean，里面方法上加@Bean注解实现Bean的注入，可以指定feign客户端的各种配置，包括Encoder/Decoder/Contract/Feign.Builder等。不同的客户端指定不同配置类，就需要对配置类进行隔离，FeignContext就是用于隔离配置的。</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">FeignContext</span> <span class="keyword">extends</span> <span class="title">NamedContextFactory</span><<span class="title">FeignClientSpecification</span>> </span>{</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="title">FeignContext</span><span class="params">()</span> </span>{</span><br><span class="line"><span class="keyword">super</span>(FeignClientsConfiguration.class, <span class="string">"feign"</span>, <span class="string">"feign.client.name"</span>);</span><br><span class="line">}</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>FeignContext继承NamedContextFactory，空参数构造函数指定FeignClientsConfiguration类为默认配置。<br>NamedContextFactory实现接口ApplicationContextAware，注入ApplicationContextAware作为parent：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">abstract</span> <span class="class"><span class="keyword">class</span> <span class="title">NamedContextFactory</span><<span class="title">C</span> <span class="keyword">extends</span> <span class="title">NamedContextFactory</span>.<span class="title">Specification</span>></span></span><br><span class="line"><span class="class"><span class="keyword">implements</span> <span class="title">DisposableBean</span>, <span class="title">ApplicationContextAware</span> </span>{</span><br><span class="line"><span class="comment">//命名空间对应的Spring Context</span></span><br><span class="line"><span class="keyword">private</span> Map<String, AnnotationConfigApplicationContext> contexts = <span class="keyword">new</span> ConcurrentHashMap<>();</span><br><span class="line"><span class="comment">//不同命名空间的定义</span></span><br><span class="line"><span class="keyword">private</span> Map<String, C> configurations = <span class="keyword">new</span> ConcurrentHashMap<>();</span><br><span class="line"><span class="comment">//父ApplicationContext，通过ApplicationContextAware接口注入</span></span><br><span class="line"><span class="keyword">private</span> ApplicationContext parent;</span><br><span class="line"><span class="comment">//默认配置类</span></span><br><span class="line"><span class="keyword">private</span> Class<?> defaultConfigType;</span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> String propertySourceName;</span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> String propertyName;</span><br><span class="line">。。。</span><br><span class="line"><span class="comment">//设置配置，在FeignAutoConfiguration中将Spring Context中的所有FeignClientSpecification设置进来，如果@EnableFeignClients有设置参数defaultConfiguration也会加进来，前面已经分析在registerDefaultConfiguration方法中注册的FeignClientSpecification Bean</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setConfigurations</span><span class="params">(List<C> configurations)</span> </span>{</span><br><span class="line"><span class="keyword">for</span> (C client : configurations) {</span><br><span class="line"><span class="keyword">this</span>.configurations.put(client.getName(), client);</span><br><span class="line">}</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//获取指定命名空间的ApplicationContext，先从缓存中获取，没有就创建</span></span><br><span class="line"><span class="function"><span class="keyword">protected</span> AnnotationConfigApplicationContext <span class="title">getContext</span><span class="params">(String name)</span> </span>{</span><br><span class="line"><span class="keyword">if</span> (!<span class="keyword">this</span>.contexts.containsKey(name)) {</span><br><span class="line"><span class="keyword">synchronized</span> (<span class="keyword">this</span>.contexts) {</span><br><span class="line"><span class="keyword">if</span> (!<span class="keyword">this</span>.contexts.containsKey(name)) {</span><br><span class="line"><span class="keyword">this</span>.contexts.put(name, createContext(name));</span><br><span class="line">}</span><br><span class="line">}</span><br><span class="line">}</span><br><span class="line"><span class="keyword">return</span> <span class="keyword">this</span>.contexts.get(name);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//创建ApplicationContext</span></span><br><span class="line"><span class="function"><span class="keyword">protected</span> AnnotationConfigApplicationContext <span class="title">createContext</span><span class="params">(String name)</span> </span>{</span><br><span class="line"><span class="comment">//新建AnnotationConfigApplicationContext</span></span><br><span class="line">AnnotationConfigApplicationContext context = <span class="keyword">new</span> AnnotationConfigApplicationContext();</span><br><span class="line"><span class="comment">//根据name在configurations找到所有的配置类，注册到context总</span></span><br><span class="line"><span class="keyword">if</span> (<span class="keyword">this</span>.configurations.containsKey(name)) {</span><br><span class="line"><span class="keyword">for</span> (Class<?> configuration : <span class="keyword">this</span>.configurations.get(name)</span><br><span class="line">.getConfiguration()) {</span><br><span class="line">context.register(configuration);</span><br><span class="line">}</span><br><span class="line">}</span><br><span class="line"><span class="comment">//将default.开头的默认默认也注册到Context中</span></span><br><span class="line"><span class="keyword">for</span> (Map.Entry<String, C> entry : <span class="keyword">this</span>.configurations.entrySet()) {</span><br><span class="line"><span class="keyword">if</span> (entry.getKey().startsWith(<span class="string">"default."</span>)) {</span><br><span class="line"><span class="keyword">for</span> (Class<?> configuration : entry.getValue().getConfiguration()) {</span><br><span class="line">context.register(configuration);</span><br><span class="line">}</span><br><span class="line">}</span><br><span class="line">}</span><br><span class="line"><span class="comment">//注册一些需要的bean</span></span><br><span class="line">context.register(PropertyPlaceholderAutoConfiguration.class,</span><br><span class="line"><span class="keyword">this</span>.defaultConfigType);</span><br><span class="line">context.getEnvironment().getPropertySources().addFirst(<span class="keyword">new</span> MapPropertySource(</span><br><span class="line"><span class="keyword">this</span>.propertySourceName,</span><br><span class="line">Collections.<String, Object> singletonMap(<span class="keyword">this</span>.propertyName, name)));</span><br><span class="line"><span class="keyword">if</span> (<span class="keyword">this</span>.parent != <span class="keyword">null</span>) {</span><br><span class="line"><span class="comment">// 设置parent</span></span><br><span class="line">context.setParent(<span class="keyword">this</span>.parent);</span><br><span class="line">}</span><br><span class="line"><span class="comment">//刷新，完成bean生成</span></span><br><span class="line">context.refresh();</span><br><span class="line"><span class="keyword">return</span> context;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//从命名空间中获取指定类型的Bean</span></span><br><span class="line"><span class="keyword">public</span> <T> <span class="function">T <span class="title">getInstance</span><span class="params">(String name, Class<T> type)</span> </span>{</span><br><span class="line">AnnotationConfigApplicationContext context = getContext(name);</span><br><span class="line"><span class="keyword">if</span> (BeanFactoryUtils.beanNamesForTypeIncludingAncestors(context,</span><br><span class="line">type).length > <span class="number">0</span>) {</span><br><span class="line"><span class="keyword">return</span> context.getBean(type);</span><br><span class="line">}</span><br><span class="line"><span class="keyword">return</span> <span class="keyword">null</span>;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//从命名空间中获取指定类型的Bean</span></span><br><span class="line"><span class="keyword">public</span> <T> <span class="function">Map<String, T> <span class="title">getInstances</span><span class="params">(String name, Class<T> type)</span> </span>{</span><br><span class="line">AnnotationConfigApplicationContext context = getContext(name);</span><br><span class="line"><span class="keyword">if</span> (BeanFactoryUtils.beanNamesForTypeIncludingAncestors(context,</span><br><span class="line">type).length > <span class="number">0</span>) {</span><br><span class="line"><span class="keyword">return</span> BeanFactoryUtils.beansOfTypeIncludingAncestors(context, type);</span><br><span class="line">}</span><br><span class="line"><span class="keyword">return</span> <span class="keyword">null</span>;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>关键的方法是createContext，为每个命名空间独立创建ApplicationContext，设置parent为外部传入的Context，这样就可以共用外部的Context中的Bean，又有各种独立的配置Bean，熟悉springMVC的同学应该知道，springMVC中创建的WebApplicatonContext里面也有个parent，原理跟这个类似。</p><p>从FeignContext中获取Bean，需要传入命名空间，根据命名空间找到缓存中的ApplicationContext，先从自己注册的Bean中获取bean，没有获取到再从到parent中获取。</p><h3 id="创建Feign-Builder"><a href="#创建Feign-Builder" class="headerlink" title="创建Feign.Builder"></a>创建Feign.Builder</h3><p>了解了FeignContext的原理，我们再来看feign最重要的构建类创建过程<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">protected</span> Feign.<span class="function">Builder <span class="title">feign</span><span class="params">(FeignContext context)</span> </span>{</span><br><span class="line">。。。</span><br><span class="line"><span class="comment">//从FeignContext中获取注册的Feign.Builder bean，设置Encoder/Decoder/Contract</span></span><br><span class="line">Feign.Builder builder = get(context, Feign.Builder.class)</span><br><span class="line">.logger(logger)</span><br><span class="line">.encoder(get(context, Encoder.class))</span><br><span class="line">.decoder(get(context, Decoder.class))</span><br><span class="line">.contract(get(context, Contract.class));</span><br><span class="line">。。。</span><br><span class="line"><span class="comment">//设置feign其他参数，都从FeignContext中获取</span></span><br><span class="line">Retryer retryer = getOptional(context, Retryer.class);</span><br><span class="line"><span class="keyword">if</span> (retryer != <span class="keyword">null</span>) {</span><br><span class="line">builder.retryer(retryer);</span><br><span class="line">}</span><br><span class="line">ErrorDecoder errorDecoder = getOptional(context, ErrorDecoder.class);</span><br><span class="line"><span class="keyword">if</span> (errorDecoder != <span class="keyword">null</span>) {</span><br><span class="line">builder.errorDecoder(errorDecoder);</span><br><span class="line">}</span><br><span class="line">Request.Options options = getOptional(context, Request.Options.class);</span><br><span class="line"><span class="keyword">if</span> (options != <span class="keyword">null</span>) {</span><br><span class="line">builder.options(options);</span><br><span class="line">}</span><br><span class="line">Map<String, RequestInterceptor> requestInterceptors = context.getInstances(</span><br><span class="line"><span class="keyword">this</span>.name, RequestInterceptor.class);</span><br><span class="line"><span class="keyword">if</span> (requestInterceptors != <span class="keyword">null</span>) {</span><br><span class="line">builder.requestInterceptors(requestInterceptors.values());</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="keyword">if</span> (decode404) {</span><br><span class="line">builder.decode404();</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="keyword">return</span> builder;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>这里设置了Feign.Builder所必须的参数Encoder/Decoder/Contract，其他参数都是可选的。这三个必须的参数从哪里来的呢？答案是在FeignContext的构造器中，传入了默认的配置FeignClientsConfiguration，这个配置类里面初始化了这三个参数。</p><h3 id="FeignClientsConfiguration-客户端默认配置"><a href="#FeignClientsConfiguration-客户端默认配置" class="headerlink" title="FeignClientsConfiguration 客户端默认配置"></a>FeignClientsConfiguration 客户端默认配置</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">FeignClientsConfiguration</span> </span>{</span><br><span class="line"><span class="comment">//注入springMVC的HttpMessageConverters</span></span><br><span class="line"><span class="meta">@Autowired</span></span><br><span class="line"><span class="keyword">private</span> ObjectFactory<HttpMessageConverters> messageConverters;</span><br><span class="line"><span class="comment">//注解参数处理器，处理SpringMVC注解，生成http元数据</span></span><br><span class="line"><span class="meta">@Autowired</span>(required = <span class="keyword">false</span>)</span><br><span class="line"><span class="keyword">private</span> List<AnnotatedParameterProcessor> parameterProcessors = <span class="keyword">new</span> ArrayList<>();</span><br><span class="line">。。。</span><br><span class="line"><span class="comment">//Decoder bean，默认通过HttpMessageConverters进行处理</span></span><br><span class="line"><span class="meta">@Bean</span></span><br><span class="line"><span class="meta">@ConditionalOnMissingBean</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> Decoder <span class="title">feignDecoder</span><span class="params">()</span> </span>{</span><br><span class="line"><span class="keyword">return</span> <span class="keyword">new</span> ResponseEntityDecoder(<span class="keyword">new</span> SpringDecoder(<span class="keyword">this</span>.messageConverters));</span><br><span class="line">}</span><br><span class="line"><span class="comment">//Encoder bean，默认通过HttpMessageConverters进行处理</span></span><br><span class="line"><span class="meta">@Bean</span></span><br><span class="line"><span class="meta">@ConditionalOnMissingBean</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> Encoder <span class="title">feignEncoder</span><span class="params">()</span> </span>{</span><br><span class="line"><span class="keyword">return</span> <span class="keyword">new</span> SpringEncoder(<span class="keyword">this</span>.messageConverters);</span><br><span class="line">}</span><br><span class="line"><span class="comment">//Contract bean，通过SpringMvcContract进行处理接口</span></span><br><span class="line"><span class="meta">@Bean</span></span><br><span class="line"><span class="meta">@ConditionalOnMissingBean</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> Contract <span class="title">feignContract</span><span class="params">(ConversionService feignConversionService)</span> </span>{</span><br><span class="line"><span class="keyword">return</span> <span class="keyword">new</span> SpringMvcContract(<span class="keyword">this</span>.parameterProcessors, feignConversionService);</span><br><span class="line">}</span><br><span class="line"><span class="comment">//hystrix自动注入</span></span><br><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="meta">@ConditionalOnClass</span>({ HystrixCommand.class, HystrixFeign.class })</span><br><span class="line"><span class="keyword">protected</span> <span class="keyword">static</span> <span class="class"><span class="keyword">class</span> <span class="title">HystrixFeignConfiguration</span> </span>{</span><br><span class="line"><span class="comment">//HystrixFeign的builder，全局关掉Hystrix配置feign.hystrix.enabled=false</span></span><br><span class="line"><span class="meta">@Bean</span></span><br><span class="line"><span class="meta">@Scope</span>(<span class="string">"prototype"</span>)</span><br><span class="line"><span class="meta">@ConditionalOnMissingBean</span></span><br><span class="line"><span class="meta">@ConditionalOnProperty</span>(name = <span class="string">"feign.hystrix.enabled"</span>, matchIfMissing = <span class="keyword">true</span>)</span><br><span class="line"><span class="keyword">public</span> Feign.<span class="function">Builder <span class="title">feignHystrixBuilder</span><span class="params">()</span> </span>{</span><br><span class="line"><span class="keyword">return</span> HystrixFeign.builder();</span><br><span class="line">}</span><br><span class="line">}</span><br><span class="line"><span class="comment">//默认不重试</span></span><br><span class="line"><span class="meta">@Bean</span></span><br><span class="line"><span class="meta">@ConditionalOnMissingBean</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> Retryer <span class="title">feignRetryer</span><span class="params">()</span> </span>{</span><br><span class="line"><span class="keyword">return</span> Retryer.NEVER_RETRY;</span><br><span class="line">}</span><br><span class="line"><span class="comment">//默认的builder</span></span><br><span class="line"><span class="meta">@Bean</span></span><br><span class="line"><span class="meta">@Scope</span>(<span class="string">"prototype"</span>)</span><br><span class="line"><span class="meta">@ConditionalOnMissingBean</span></span><br><span class="line"><span class="keyword">public</span> Feign.<span class="function">Builder <span class="title">feignBuilder</span><span class="params">(Retryer retryer)</span> </span>{</span><br><span class="line"><span class="keyword">return</span> Feign.builder().retryer(retryer);</span><br><span class="line">}</span><br><span class="line">。。。</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>可以看到，feign需要的decoder/enoder通过适配器共用springMVC中的HttpMessageConverters引入。</p><p>feign有自己的注解体系，这里通过SpringMvcContract适配了springMVC的注解体系。</p><h3 id="SpringMvcContract-适配feign注解体系"><a href="#SpringMvcContract-适配feign注解体系" class="headerlink" title="SpringMvcContract 适配feign注解体系"></a>SpringMvcContract 适配feign注解体系</h3><p>SpringMvcContract继承了feign的类Contract.BaseContract，作用是解析接口方法上的注解和方法参数，生成MethodMetadata用于接口方法调用过程中组装http请求。</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">SpringMvcContract</span> <span class="keyword">extends</span> <span class="title">Contract</span>.<span class="title">BaseContract</span></span></span><br><span class="line"><span class="class"><span class="keyword">implements</span> <span class="title">ResourceLoaderAware</span> </span>{</span><br><span class="line">。。。</span><br><span class="line"></span><br><span class="line"><span class="comment">//处理Class上的注解</span></span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title">processAnnotationOnClass</span><span class="params">(MethodMetadata data, Class<?> clz)</span> </span>{</span><br><span class="line">。。。</span><br><span class="line">}</span><br><span class="line"><span class="comment">//处理方法</span></span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> MethodMetadata <span class="title">parseAndValidateMetadata</span><span class="params">(Class<?> targetType, Method method)</span> </span>{</span><br><span class="line">。。。</span><br><span class="line">}</span><br><span class="line"><span class="comment">//处理方法上的注解</span></span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title">processAnnotationOnMethod</span><span class="params">(MethodMetadata data,</span></span></span><br><span class="line"><span class="function"><span class="params">Annotation methodAnnotation, Method method)</span> </span>{</span><br><span class="line"> 。。。</span><br><span class="line">}</span><br><span class="line"><span class="comment">//处理参数上的注解</span></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">protected</span> <span class="keyword">boolean</span> <span class="title">processAnnotationsOnParameter</span><span class="params">(MethodMetadata data,</span></span></span><br><span class="line"><span class="function"><span class="params"> Annotation[] annotations, <span class="keyword">int</span> paramIndex)</span> </span>{</span><br><span class="line"> 。。。</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>几个覆盖方法分别是处理类上的注解，处理方法，处理方法上的注解，处理方法参数注解，最终生成完整的MethodMetadata。feign自己提供的Contract和扩展javax.ws.rx的Contract原理都是类似的。</p><h3 id="Targeter-生成接口动态代理"><a href="#Targeter-生成接口动态代理" class="headerlink" title="Targeter 生成接口动态代理"></a>Targeter 生成接口动态代理</h3><p>Feign.Builder生成后，就要用Target生成feign客户端的动态代理，这里FeignClientFactoryBean中使用Targeter，Targeter有两个实现类，分别是HystrixTargeter和DefaultTargeter，DefaultTargeter很简单，直接调用HardCodedTarget生成动态代理，HystrixTargeter源码如下：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">HystrixTargeter</span> <span class="keyword">implements</span> <span class="title">Targeter</span> </span>{</span><br><span class="line"></span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="keyword">public</span> <T> <span class="function">T <span class="title">target</span><span class="params">(FeignClientFactoryBean factory, Feign.Builder feign, FeignContext context,</span></span></span><br><span class="line"><span class="function"><span class="params">Target.HardCodedTarget<T> target)</span> </span>{</span><br><span class="line"><span class="comment">//如果不是HystrixFeign.Builder，直接调用target生成代理</span></span><br><span class="line"><span class="keyword">if</span> (!(feign <span class="keyword">instanceof</span> feign.hystrix.HystrixFeign.Builder)) {</span><br><span class="line"><span class="keyword">return</span> feign.target(target);</span><br><span class="line">}</span><br><span class="line"><span class="comment">//找到fallback或者fallbackFactory，设置到hystrix中</span></span><br><span class="line">feign.hystrix.HystrixFeign.Builder builder = (feign.hystrix.HystrixFeign.Builder) feign;</span><br><span class="line">Class<?> fallback = factory.getFallback();</span><br><span class="line"><span class="keyword">if</span> (fallback != <span class="keyword">void</span>.class) {</span><br><span class="line"><span class="keyword">return</span> targetWithFallback(factory.getName(), context, target, builder, fallback);</span><br><span class="line">}</span><br><span class="line">Class<?> fallbackFactory = factory.getFallbackFactory();</span><br><span class="line"><span class="keyword">if</span> (fallbackFactory != <span class="keyword">void</span>.class) {</span><br><span class="line"><span class="keyword">return</span> targetWithFallbackFactory(factory.getName(), context, target, builder, fallbackFactory);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="keyword">return</span> feign.target(target);</span><br><span class="line">}</span><br><span class="line"> 。。。</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>到这里，接口的动态代理就生成了，然后回到FeignClientFactoryBean工厂bean中，会将动态代理注入到SpringContext，在使用的地方，就可以通过@Autowire方式注入了。</p><h2 id="loadBalance方法，客户端负载均衡"><a href="#loadBalance方法，客户端负载均衡" class="headerlink" title="loadBalance方法，客户端负载均衡"></a>loadBalance方法，客户端负载均衡</h2><p>如果@FeignClient注解中没有配置url参数，将会通过loadBalance方法生成Ribbon的动态代理：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">protected</span> <T> <span class="function">T <span class="title">loadBalance</span><span class="params">(Feign.Builder builder, FeignContext context,</span></span></span><br><span class="line"><span class="function"><span class="params">HardCodedTarget<T> target)</span> </span>{</span><br><span class="line"><span class="comment">//这里获取到的Client是LoadBalancerFeignClient</span></span><br><span class="line">Client client = getOptional(context, Client.class);</span><br><span class="line"><span class="keyword">if</span> (client != <span class="keyword">null</span>) {</span><br><span class="line">builder.client(client);</span><br><span class="line">Targeter targeter = get(context, Targeter.class);</span><br><span class="line"><span class="keyword">return</span> targeter.target(<span class="keyword">this</span>, builder, context, target);</span><br><span class="line">}</span><br><span class="line">。。。</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>LoadBalancerFeignClient在FeignRibbonClientAutoConfiguration中自动配置的Bean</p><h3 id="LoadBalancerFeignClient-负载均衡客户端"><a href="#LoadBalancerFeignClient-负载均衡客户端" class="headerlink" title="LoadBalancerFeignClient 负载均衡客户端"></a>LoadBalancerFeignClient 负载均衡客户端</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">LoadBalancerFeignClient</span> <span class="keyword">implements</span> <span class="title">Client</span> </span>{</span><br><span class="line">。。。</span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> Response <span class="title">execute</span><span class="params">(Request request, Request.Options options)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"><span class="keyword">try</span> {</span><br><span class="line"><span class="comment">//获取URI</span></span><br><span class="line">URI asUri = URI.create(request.url());</span><br><span class="line"><span class="comment">//获取客户端的名称</span></span><br><span class="line">String clientName = asUri.getHost();</span><br><span class="line">URI uriWithoutHost = cleanUrl(request.url(), clientName);</span><br><span class="line"><span class="comment">//创建RibbonRequest</span></span><br><span class="line">FeignLoadBalancer.RibbonRequest ribbonRequest = <span class="keyword">new</span> FeignLoadBalancer.RibbonRequest(</span><br><span class="line"><span class="keyword">this</span>.delegate, request, uriWithoutHost);</span><br><span class="line"><span class="comment">//配置</span></span><br><span class="line">IClientConfig requestConfig = getClientConfig(options, clientName);</span><br><span class="line"><span class="comment">//获取FeignLoadBalancer，发请求，转换Response</span></span><br><span class="line"><span class="keyword">return</span> lbClient(clientName).executeWithLoadBalancer(ribbonRequest,</span><br><span class="line">requestConfig).toResponse();</span><br><span class="line">} <span class="keyword">catch</span> (ClientException e) {</span><br><span class="line">。。。</span><br><span class="line">}</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>代码逻辑也比较简单，就是是配到Ribbon客户端上调用。Ribbon的相关使用和原理就不在本文中描述。</p><h1 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h1><p>feign本身是一款优秀的开源组件，spring cloud feign又非常巧妙的将feign集成到spring boot中。<br>本文通过对spring cloud feign源代码的解读，详细的分析了feign集成到spring boot中的原理，使我们更加全面的了解到feign的使用。</p><p>spring cloud feign也是一个很好的学习spring boot的例子，从中我们可以学习到：</p><ul><li>spring boot注解声明注入bean</li><li>spring类扫描机制</li><li>spring接口动态注册bean</li><li>spring命名空间隔离ApplicationContext</li></ul>]]></content>
<summary type="html">
<h1 id="简介"><a href="#简介" class="headerlink" title="简介"></a>简介</h1><p><a href="https://github.com/OpenFeign/feign" target="_blank" rel="noopener">feign</a>是一个声明试的HTTP客户端，spring-cloud-openfeign将feign集成到spring boot中，在接口上通过注解声明Rest协议，将http调用转换为接口方法的调用，使得客户端调用http服务更加简单。</p>
<p>当前spring cloud最新稳定版本是Edgware，feign在其集成的<a href="https://github.com/spring-cloud/spring-cloud-netflix" target="_blank" rel="noopener">spring-cloud-netflix</a> 1.4.0.RELEASE版本中。</p>
<blockquote>
<p>spring cloud下一个版本是Finchley，将会单独集成<a href="https://github.com/spring-cloud/spring-cloud-openfeign" target="_blank" rel="noopener">spring-cloud-openfeign</a></p>
</blockquote>
</summary>
<category term="spring" scheme="http://along101.site/categories/spring/"/>
<category term="rest" scheme="http://along101.site/tags/rest/"/>
<category term="feign" scheme="http://along101.site/tags/feign/"/>
<category term="spring-cloud" scheme="http://along101.site/tags/spring-cloud/"/>
</entry>
<entry>
<title>Feign使用教程，翻译版本</title>
<link href="http://along101.site/2018/06/14/feign-user-guide/"/>
<id>http://along101.site/2018/06/14/feign-user-guide/</id>
<published>2018-06-14T12:03:13.000Z</published>
<updated>2018-07-20T03:10:04.405Z</updated>
<content type="html"><![CDATA[<p>英文原文请参考:<a href="https://github.com/OpenFeign/feign" target="_blank" rel="noopener">https://github.com/OpenFeign/feign</a><br>翻译参考:<a href="https://blog.csdn.net/u010862794/article/details/73649616" target="_blank" rel="noopener">https://blog.csdn.net/u010862794/article/details/73649616</a></p><h2 id="简介"><a href="#简介" class="headerlink" title="简介"></a>简介</h2><p>Feign是一款java的Restful客户端组件，Feign使得 Java HTTP 客户端编写更方便。Feign 灵感来源于<a href="https://github.com/square/retrofit" target="_blank" rel="noopener">Retrofit</a>, <a href="https://jax-rs-spec.java.net/nonav/2.0/apidocs/index.html" target="_blank" rel="noopener">JAXRS-2.0</a>和<a href="http://www.oracle.com/technetwork/articles/java/jsr356-1937161.html" target="_blank" rel="noopener">WebSocket</a>。Feign 最初是为了降低统一绑定<a href="https://github.com/Netflix/Denominator" target="_blank" rel="noopener">Denominator</a> 到 HTTP API 的复杂度，不区分是否支持 <a href="http://www.slideshare.net/adrianfcole/99problems" target="_blank" rel="noopener">ReSTfulness</a>。</p><a id="more"></a><h3 id="为什么选择Feign而不是其他"><a href="#为什么选择Feign而不是其他" class="headerlink" title="为什么选择Feign而不是其他"></a>为什么选择Feign而不是其他</h3><p>你可以使用 Jersey 和 CXF 这些来写一个 Rest 或 SOAP 服务的java客服端。你也可以直接使用 Apache HttpClient 来实现。但是 Feign 的目的是尽量的减少资源和代码来实现和 HTTP API 的连接。通过自定义的编码解码器以及错误处理，你可以编写任何基于文本的 HTTP API。</p><h3 id="Feign工作机制"><a href="#Feign工作机制" class="headerlink" title="Feign工作机制"></a>Feign工作机制</h3><p>Feign 通过注解注入一个模板化请求进行工作。只需在发送之前关闭它，参数就可以被直接的运用到模板中。然而这也限制了 Feign，只支持文本形式的API，它在响应请求等方面极大的简化了系统。同时，它也是十分容易进行单元测试的。</p><h3 id="基本用法"><a href="#基本用法" class="headerlink" title="基本用法"></a>基本用法</h3><p>基本的使用如下所示，一个对于<a href="https://github.com/square/retrofit/blob/master/samples/src/main/java/com/example/retrofit/SimpleService.java" target="_blank" rel="noopener">canonical Retrofit sample</a>的适配。</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">GitHub</span> </span>{</span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"GET /repos/{owner}/{repo}/contributors"</span>)</span><br><span class="line"> <span class="function">List<Contributor> <span class="title">contributors</span><span class="params">(@Param(<span class="string">"owner"</span>)</span> String owner, @<span class="title">Param</span><span class="params">(<span class="string">"repo"</span>)</span> String repo)</span>;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="keyword">static</span> <span class="class"><span class="keyword">class</span> <span class="title">Contributor</span> </span>{</span><br><span class="line"> String login;</span><br><span class="line"> <span class="keyword">int</span> contributions;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String... args)</span> </span>{</span><br><span class="line"> GitHub github = Feign.builder()</span><br><span class="line"> .decoder(<span class="keyword">new</span> GsonDecoder())</span><br><span class="line"> .target(GitHub.class, <span class="string">"https://api.github.com"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// Fetch and print a list of the contributors to this library.</span></span><br><span class="line"> List<Contributor> contributors = github.contributors(<span class="string">"OpenFeign"</span>, <span class="string">"feign"</span>);</span><br><span class="line"> <span class="keyword">for</span> (Contributor contributor : contributors) {</span><br><span class="line"> System.out.println(contributor.login + <span class="string">" ("</span> + contributor.contributions + <span class="string">")"</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="自定义"><a href="#自定义" class="headerlink" title="自定义"></a>自定义</h3><p>Feign 有许多可以自定义的方面。举个简单的例子，你可以使用 <code>Feign.builder()</code> 来构造一个拥有你自己组件的API接口。如下:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">Bank</span> </span>{</span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"POST /account/{id}"</span>)</span><br><span class="line"> <span class="function">Account <span class="title">getAccountInfo</span><span class="params">(@Param(<span class="string">"id"</span>)</span> String id)</span>;</span><br><span class="line">}</span><br><span class="line">...</span><br><span class="line"><span class="comment">// AccountDecoder 是自己实现的一个Decoder</span></span><br><span class="line">Bank bank = Feign.builder().decoder(<span class="keyword">new</span> AccountDecoder()).target(Bank.class, <span class="string">"https://api.examplebank.com"</span>);</span><br></pre></td></tr></table></figure></p><h3 id="多种接口"><a href="#多种接口" class="headerlink" title="多种接口"></a>多种接口</h3><p>Feign可以提供多种API接口，这些接口都被定义为 <code>Target<T></code> (默认的实现是 <code>HardCodedTarget<T></code>), 它允许在执行请求前动态发现和装饰该请求。</p><p>举个例子，下面的这个模式允许使用当前url和身份验证token来装饰每个发往身份验证中心服务的请求。<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">CloudDNS cloudDNS = Feign.builder().target(<span class="keyword">new</span> CloudIdentityTarget<CloudDNS>(user, apiKey));</span><br></pre></td></tr></table></figure></p><h3 id="示例"><a href="#示例" class="headerlink" title="示例"></a>示例</h3><p>Feign 包含了 <a href="./example-github">GitHub</a> 和 <a href="./example-wikipedia">Wikipedia</a> 客户端的实现样例.相似的项目也同样在实践中运用了Feign。尤其是它的示例后台程序<a href="https://github.com/Netflix/denominator/tree/master/example-daemon" target="_blank" rel="noopener">example daemon</a>。</p><h3 id="Feign集成模块"><a href="#Feign集成模块" class="headerlink" title="Feign集成模块"></a>Feign集成模块</h3><p>Feign 可以和其他的开源工具集成工作。你可以将这些开源工具集成到 Feign 中来。目前已经有的一些模块如下:</p><h3 id="Gson"><a href="#Gson" class="headerlink" title="Gson"></a>Gson</h3><p>Gson 包含了一个编码器和一个解码器，这个可以被用于JSON格式的API。<br>添加 <code>GsonEncoder</code> 以及 <code>GsonDecoder</code> 到你的 <code>Feign.Builder</code> 中， 如下:</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">GsonCodec codec = <span class="keyword">new</span> GsonCodec();</span><br><span class="line">GitHub github = Feign.builder()</span><br><span class="line"> .encoder(<span class="keyword">new</span> GsonEncoder())</span><br><span class="line"> .decoder(<span class="keyword">new</span> GsonDecoder())</span><br><span class="line"> .target(GitHub.class, <span class="string">"https://api.github.com"</span>);</span><br></pre></td></tr></table></figure><h3 id="Jackson"><a href="#Jackson" class="headerlink" title="Jackson"></a>Jackson</h3><p>Jackson 包含了一个编码器和一个解码器，这个可以被用于JSON格式的API。<br>添加 <code>JacksonEncoder</code> 以及 <code>JacksonDecoder</code> 到你的 <code>Feign.Builder</code> 中， 如下:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">GitHub github = Feign.builder()</span><br><span class="line"> .encoder(<span class="keyword">new</span> JacksonEncoder())</span><br><span class="line"> .decoder(<span class="keyword">new</span> JacksonDecoder())</span><br><span class="line"> .target(GitHub.class, <span class="string">"https://api.github.com"</span>);</span><br></pre></td></tr></table></figure></p><p>Maven依赖:</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment"><!-- https://mvnrepository.com/artifact/com.netflix.feign/feign-gson --></span></span><br><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>com.netflix.feign<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>feign-jackson<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>8.18.0<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependency</span>></span></span><br></pre></td></tr></table></figure><h3 id="Sax"><a href="#Sax" class="headerlink" title="Sax"></a>Sax</h3><p>SaxDecoder 用于解析XML,并兼容普通JVM和Android。下面是一个配置sax来解析响应的例子:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">api = Feign.builder()</span><br><span class="line"> .decoder(SAXDecoder.builder()</span><br><span class="line"> .registerContentHandler(UserIdHandler.class)</span><br><span class="line"> .build())</span><br><span class="line"> .target(Api.class, <span class="string">"https://apihost"</span>);</span><br></pre></td></tr></table></figure></p><p>Maven依赖:<br><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>com.netflix.feign<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>feign-sax<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>8.18.0<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependency</span>></span></span><br></pre></td></tr></table></figure></p><h3 id="JAXB"><a href="#JAXB" class="headerlink" title="JAXB"></a>JAXB</h3><p>JAXB 包含了一个编码器和一个解码器，这个可以被用于XML格式的API。<br>添加 <code>JAXBEncoder</code> 以及 <code>JAXBDecoder</code> 到你的 <code>Feign.Builder</code> 中， 如下:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">api = Feign.builder()</span><br><span class="line"> .encoder(<span class="keyword">new</span> JAXBEncoder())</span><br><span class="line"> .decoder(<span class="keyword">new</span> JAXBDecoder())</span><br><span class="line"> .target(Api.class, <span class="string">"https://apihost"</span>);</span><br></pre></td></tr></table></figure></p><p>Maven依赖:<br><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment"><!-- https://mvnrepository.com/artifact/com.netflix.feign/feign-gson --></span></span><br><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>com.netflix.feign<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>feign-jaxb<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>8.18.0<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependency</span>></span></span><br></pre></td></tr></table></figure></p><h3 id="JAX-RS"><a href="#JAX-RS" class="headerlink" title="JAX-RS"></a>JAX-RS</h3><p>JAXRSContract 使用 JAX-RS 规范重写覆盖了默认的注解处理。下面是一个使用 JAX-RS 的例子:</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">GitHub</span> </span>{</span><br><span class="line"> <span class="meta">@GET</span> <span class="meta">@Path</span>(<span class="string">"/repos/{owner}/{repo}/contributors"</span>)</span><br><span class="line"> <span class="function">List<Contributor> <span class="title">contributors</span><span class="params">(@PathParam(<span class="string">"owner"</span>)</span> String owner, @<span class="title">PathParam</span><span class="params">(<span class="string">"repo"</span>)</span> String repo)</span>;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">GitHub github = Feign.builder()</span><br><span class="line"> .contract(<span class="keyword">new</span> JAXRSContract())</span><br><span class="line"> .target(GitHub.class, <span class="string">"https://api.github.com"</span>);</span><br></pre></td></tr></table></figure><p>Maven依赖:</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment"><!-- https://mvnrepository.com/artifact/com.netflix.feign/feign-gson --></span></span><br><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>com.netflix.feign<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>feign-jaxrs<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>8.18.0<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependency</span>></span></span><br></pre></td></tr></table></figure><h3 id="OkHttp"><a href="#OkHttp" class="headerlink" title="OkHttp"></a>OkHttp</h3><p>OkHttpClient 使用 OkHttp 来发送 Feign 的请求，OkHttp 支持 SPDY (SPDY是Google开发的基于TCP的传输层协议，用以最小化网络延迟，提升网络速度，优化用户的网络使用体验),并有更好的控制http请求。</p><p>要让 Feign 使用 OkHttp ，你需要将 OkHttp 加入到你的环境变量中区，然后配置 Feign 使用 <code>OkHttpClient</code>，如下:</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">GitHub github = Feign.builder()</span><br><span class="line"> .client(<span class="keyword">new</span> OkHttpClient())</span><br><span class="line"> .target(GitHub.class, <span class="string">"https://api.github.com"</span>);</span><br></pre></td></tr></table></figure><p>Maven依赖:<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><!-- https://mvnrepository.com/artifact/com.netflix.feign/feign-gson --></span><br><span class="line"><dependency></span><br><span class="line"> <groupId>com.netflix.feign</groupId></span><br><span class="line"> <artifactId>feign-okhttp</artifactId></span><br><span class="line"> <version>8.18.0</version></span><br><span class="line"></dependency></span><br></pre></td></tr></table></figure></p><h3 id="Ribbon"><a href="#Ribbon" class="headerlink" title="Ribbon"></a>Ribbon</h3><p>RibbonClient 重写了 Feign 客户端的对URL的处理，其添加了 智能路由以及一些其他由Ribbon提供的弹性功能。<br>集成Ribbon需要你将ribbon的客户端名称当做url的host部分来传递，如下：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// myAppProd是你的ribbon client name</span></span><br><span class="line">MyService api = Feign.builder().client(RibbonClient.create()).target(MyService.class, <span class="string">"https://myAppProd"</span>);</span><br></pre></td></tr></table></figure></p><p>Maven依赖:<br><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment"><!-- https://mvnrepository.com/artifact/com.netflix.feign/feign-gson --></span></span><br><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>com.netflix.feign<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>feign-ribbon<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>8.18.0<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependency</span>></span></span><br></pre></td></tr></table></figure></p><h3 id="Hystrix"><a href="#Hystrix" class="headerlink" title="Hystrix"></a>Hystrix</h3><p>HystrixFeign 配置了 Hystrix 提供的熔断机制。<br>要在 Feign 中使用 Hystrix ，你需要添加Hystrix模块到你的环境变量，然后使用 <code>HystrixFeign</code> 来构造你的API:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">MyService api = HystrixFeign.builder().target(MyService.class, <span class="string">"https://myAppProd"</span>);</span><br></pre></td></tr></table></figure></p><p>Maven依赖:<br><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment"><!-- https://mvnrepository.com/artifact/com.netflix.feign/feign-gson --></span></span><br><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>com.netflix.feign<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>feign-hystrix<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>8.18.0<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependency</span>></span></span><br></pre></td></tr></table></figure></p><h3 id="SLF4J"><a href="#SLF4J" class="headerlink" title="SLF4J"></a>SLF4J</h3><p>SLF4JModule 允许你使用 SLF4J 作为 Feign 的日志记录模块，这样你就可以轻松的使用 Logback, Log4J , 等来记录你的日志.</p><p>要在 Feign 中使用 SLF4J ，你需要添加SLF4J模块和对应的日志记录实现模块(比如Log4J)到你的环境变量，然后配置Feign使用Slf4jLogger :</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">GitHub github = Feign.builder()</span><br><span class="line"> .logger(<span class="keyword">new</span> Slf4jLogger())</span><br><span class="line"> .target(GitHub.class, <span class="string">"https://api.github.com"</span>);</span><br></pre></td></tr></table></figure><p>Maven依赖:<br><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment"><!-- https://mvnrepository.com/artifact/com.netflix.feign/feign-gson --></span></span><br><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>com.netflix.feign<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>feign-slf4j<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>8.18.0<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependency</span>></span></span><br></pre></td></tr></table></figure></p><h3 id="Decoders"><a href="#Decoders" class="headerlink" title="Decoders"></a>Decoders</h3><p> <code>Feign.builder()</code> 允许你自定义一些额外的配置，比如说如何解码一个响应。假如有接口方法返回的消息不是 <code>Response</code>, <code>String</code>, <code>byte[]</code> 或者 <code>void</code> 类型的，那么你需要配置一个非默认的解码器。<br>下面是一个配置使用JSON解码器(使用的是feign-gson扩展)的例子:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">GitHub github = Feign.builder()</span><br><span class="line"> .decoder(<span class="keyword">new</span> GsonDecoder())</span><br><span class="line"> .target(GitHub.class, <span class="string">"https://api.github.com"</span>);</span><br></pre></td></tr></table></figure></p><p>假如你想在将响应传递给解码器处理前做一些额外的处理，那么你可以使用 <code>mapAndDecode</code> 方法。一个用例就是使用jsonp服务的时候:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">JsonpApi jsonpApi = Feign.builder()</span><br><span class="line"> .mapAndDecode((response, type) -> jsopUnwrap(response, type), <span class="keyword">new</span> GsonDecoder())</span><br><span class="line"> .target(JsonpApi.class, <span class="string">"https://some-jsonp-api.com"</span>);</span><br></pre></td></tr></table></figure></p><h3 id="Encoders"><a href="#Encoders" class="headerlink" title="Encoders"></a>Encoders</h3><p>发送一个Post请求最简单的方法就是传递一个 <code>String</code> 或者 <code>byte[]</code> 类型的参数了。你也许还需添加一个<code>Content-Type</code>请求头，如下:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">LoginClient</span> </span>{</span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"POST /"</span>)</span><br><span class="line"> <span class="meta">@Headers</span>(<span class="string">"Content-Type: application/json"</span>)</span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">login</span><span class="params">(String content)</span></span>;</span><br><span class="line">}</span><br><span class="line">...</span><br><span class="line">client.login(<span class="string">"{\"user_name\": \"denominator\", \"password\": \"secret\"}"</span>);</span><br></pre></td></tr></table></figure></p><p>通过配置一个解码器，你可以发送一个安全类型的请求体，如下是一个使用 feign-gson 扩展的例子:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">static</span> <span class="class"><span class="keyword">class</span> <span class="title">Credentials</span> </span>{</span><br><span class="line"> <span class="keyword">final</span> String user_name;</span><br><span class="line"> <span class="keyword">final</span> String password;</span><br><span class="line"></span><br><span class="line"> Credentials(String user_name, String password) {</span><br><span class="line"> <span class="keyword">this</span>.user_name = user_name;</span><br><span class="line"> <span class="keyword">this</span>.password = password;</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">LoginClient</span> </span>{</span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"POST /"</span>)</span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">login</span><span class="params">(Credentials creds)</span></span>;</span><br><span class="line">}</span><br><span class="line">...</span><br><span class="line">LoginClient client = Feign.builder()</span><br><span class="line"> .encoder(<span class="keyword">new</span> GsonEncoder())</span><br><span class="line"> .target(LoginClient.class, <span class="string">"https://foo.com"</span>);</span><br><span class="line"></span><br><span class="line">client.login(<span class="keyword">new</span> Credentials(<span class="string">"denominator"</span>, <span class="string">"secret"</span>));</span><br></pre></td></tr></table></figure></p><h3 id="Body-templates"><a href="#Body-templates" class="headerlink" title="@Body templates"></a>@Body templates</h3><p><code>@Body</code>注解申明一个请求体模板，模板中可以带有参数，与方法中 <code>@Param</code> 注解申明的参数相匹配,使用方法如下<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">LoginClient</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"POST /"</span>)</span><br><span class="line"> <span class="meta">@Headers</span>(<span class="string">"Content-Type: application/xml"</span>)</span><br><span class="line"> <span class="meta">@Body</span>(<span class="string">"<login \"user_name\"=\"{user_name}\" \"password\"=\"{password}\"/>"</span>)</span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">xml</span><span class="params">(@Param(<span class="string">"user_name"</span>)</span> String user, @<span class="title">Param</span><span class="params">(<span class="string">"password"</span>)</span> String password)</span>;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"POST /"</span>)</span><br><span class="line"> <span class="meta">@Headers</span>(<span class="string">"Content-Type: application/json"</span>)</span><br><span class="line"> <span class="comment">// json curly braces must be escaped!</span></span><br><span class="line"> <span class="comment">// 这里JSON格式需要的花括号居然需要转码，有点蛋疼了。</span></span><br><span class="line"> <span class="meta">@Body</span>(<span class="string">"%7B\"user_name\": \"{user_name}\", \"password\": \"{password}\"%7D"</span>)</span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">json</span><span class="params">(@Param(<span class="string">"user_name"</span>)</span> String user, @<span class="title">Param</span><span class="params">(<span class="string">"password"</span>)</span> String password)</span>;</span><br><span class="line">}</span><br><span class="line">...</span><br><span class="line"><span class="comment">// <login "user_name"="denominator" "password"="secret"/></span></span><br><span class="line">client.xml(<span class="string">"denominator"</span>, <span class="string">"secret"</span>);</span><br><span class="line"><span class="comment">// {"user_name": "denominator", "password": "secret"}</span></span><br><span class="line">client.json(<span class="string">"denominator"</span>, <span class="string">"secret"</span>);</span><br></pre></td></tr></table></figure></p><h3 id="Headers"><a href="#Headers" class="headerlink" title="Headers"></a>Headers</h3><p>Feign 支持给请求的api设置或者请求的客户端设置请求头</p><ul><li><p>使用 <code>@Headers</code> 设置静态请求头</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 给BaseApi中的所有方法设置Accept请求头</span></span><br><span class="line"><span class="meta">@Headers</span>(<span class="string">"Accept: application/json"</span>)</span><br><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">BaseApi</span><<span class="title">V</span>> </span>{</span><br><span class="line"> <span class="comment">// 单独给put方法设置Content-Type请求头</span></span><br><span class="line"> <span class="meta">@Headers</span>(<span class="string">"Content-Type: application/json"</span>)</span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"PUT /api/{key}"</span>)</span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">put</span><span class="params">(@Param(<span class="string">"key"</span>)</span> String, V value)</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></li><li><p>设置动态值的请求头</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestLine</span>(<span class="string">"POST /"</span>)</span><br><span class="line"><span class="meta">@Headers</span>(<span class="string">"X-Ping: {token}"</span>)</span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">post</span><span class="params">(@Param(<span class="string">"token"</span>)</span> String token)</span>;</span><br></pre></td></tr></table></figure></li><li><p>设置key和value都是动态的请求头<br>有些API需要根据调用时动态确定使用不同的请求头(e.g. custom metadata header fields such as “x-amz-meta-” or “x-goog-meta-“),这时候可以使用 <code>@HeaderMap</code> 注解，如下:</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// @HeaderMap 注解设置的请求头优先于其他方式设置的</span></span><br><span class="line"><span class="meta">@RequestLine</span>(<span class="string">"POST /"</span>)</span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">post</span><span class="params">(@HeaderMap Map<String, Object> headerMap)</span></span>;</span><br></pre></td></tr></table></figure></li></ul><h3 id="给Target设置请求头"><a href="#给Target设置请求头" class="headerlink" title="给Target设置请求头"></a>给Target设置请求头</h3><p>有时我们需要在一个API实现中根据不同的endpoint来传入不同的Header，这个时候我们可以使用自定义的<code>RequestInterceptor</code> 或 <code>Target</code>来实现.<br>通过自定义的 <code>RequestInterceptor</code> 来实现请查看 <code>Request Interceptors</code> 章节.<br>下面是一个通过自定义<code>Targe</code>t来实现给每个<code>Target</code>设置安全校验信息Header的例子:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">static</span> <span class="class"><span class="keyword">class</span> <span class="title">DynamicAuthTokenTarget</span><<span class="title">T</span>> <span class="keyword">implements</span> <span class="title">Target</span><<span class="title">T</span>> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="title">DynamicAuthTokenTarget</span><span class="params">(Class<T> clazz,</span></span></span><br><span class="line"><span class="function"><span class="params"> UrlAndTokenProvider provider,</span></span></span><br><span class="line"><span class="function"><span class="params"> ThreadLocal<String> requestIdProvider)</span></span>;</span><br><span class="line"> ...</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> Request <span class="title">apply</span><span class="params">(RequestTemplate input)</span> </span>{</span><br><span class="line"> TokenIdAndPublicURL urlAndToken = provider.get();</span><br><span class="line"> <span class="keyword">if</span> (input.url().indexOf(<span class="string">"http"</span>) != <span class="number">0</span>) {</span><br><span class="line"> input.insert(<span class="number">0</span>, urlAndToken.publicURL);</span><br><span class="line"> }</span><br><span class="line"> input.header(<span class="string">"X-Auth-Token"</span>, urlAndToken.tokenId);</span><br><span class="line"> input.header(<span class="string">"X-Request-ID"</span>, requestIdProvider.get());</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> input.request();</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line">...</span><br><span class="line">Bank bank = Feign.builder()</span><br><span class="line"> .target(<span class="keyword">new</span> DynamicAuthTokenTarget(Bank.class, provider, requestIdProvider));</span><br></pre></td></tr></table></figure></p><p>这种方法的实现依赖于给Feign 客户端设置的自定义的<code>RequestInterceptor</code> 或 <code>Target</code>。可以被用来给一个客户端的所有api请求设置请求头。比如说可是被用来在header中设置身份校验信息。这些方法是在线程执行api请求的时候才会执行，所以是允许在运行时根据上下文来动态设置header的。<br>比如说可以根据线程本地存储(thread-local storage)来为不同的线程设置不同的请求头。</p><h3 id="高级用法"><a href="#高级用法" class="headerlink" title="高级用法"></a>高级用法</h3><h4 id="Base-APIS"><a href="#Base-APIS" class="headerlink" title="Base APIS"></a>Base APIS</h4><p>有些请求中的一些方法是通用的，但是可能会有不同的参数类型或者返回类型，这个时候可以这么用:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 通用API</span></span><br><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">BaseAPI</span> </span>{</span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"GET /health"</span>)</span><br><span class="line"> <span class="function">String <span class="title">health</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"GET /all"</span>)</span><br><span class="line"> <span class="function">List<Entity> <span class="title">all</span><span class="params">()</span></span>;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">// 继承通用API</span></span><br><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">CustomAPI</span> <span class="keyword">extends</span> <span class="title">BaseAPI</span> </span>{</span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"GET /custom"</span>)</span><br><span class="line"> <span class="function">String <span class="title">custom</span><span class="params">()</span></span>;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">// 各种类型有相同的表现形式，定义一个统一的API</span></span><br><span class="line"><span class="meta">@Headers</span>(<span class="string">"Accept: application/json"</span>)</span><br><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">BaseApi</span><<span class="title">V</span>> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"GET /api/{key}"</span>)</span><br><span class="line"> <span class="function">V <span class="title">get</span><span class="params">(@Param(<span class="string">"key"</span>)</span> String key)</span>;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"GET /api"</span>)</span><br><span class="line"> <span class="function">List<V> <span class="title">list</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Headers</span>(<span class="string">"Content-Type: application/json"</span>)</span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"PUT /api/{key}"</span>)</span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">put</span><span class="params">(@Param(<span class="string">"key"</span>)</span> String key, V value)</span>;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">// 根据不同的类型来继承</span></span><br><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">FooApi</span> <span class="keyword">extends</span> <span class="title">BaseApi</span><<span class="title">Foo</span>> </span>{ }</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">BarApi</span> <span class="keyword">extends</span> <span class="title">BaseApi</span><<span class="title">Bar</span>> </span>{ }</span><br></pre></td></tr></table></figure></p><h4 id="Logging"><a href="#Logging" class="headerlink" title="Logging"></a>Logging</h4><p>你可以通过设置一个 <code>Logger</code> 来记录http消息，如下:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">GitHub github = Feign.builder()</span><br><span class="line"> .decoder(<span class="keyword">new</span> GsonDecoder())</span><br><span class="line"> .logger(<span class="keyword">new</span> Logger.JavaLogger().appendToFile(<span class="string">"logs/http.log"</span>))</span><br><span class="line"> .logLevel(Logger.Level.FULL)</span><br><span class="line"> .target(GitHub.class, <span class="string">"https://api.github.com"</span>);</span><br></pre></td></tr></table></figure></p><p>也可以参考上面的 SLF4J 章节的说明</p><h4 id="Request-Interceptors"><a href="#Request-Interceptors" class="headerlink" title="Request Interceptors"></a>Request Interceptors</h4><p>当你希望修改所有的的请求的时候，你可以使用<code>Request Interceptors</code>。比如说，你作为一个中介，你可能需要为每个请求设置 <code>X-Forwarded-For</code><br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">static</span> <span class="class"><span class="keyword">class</span> <span class="title">ForwardedForInterceptor</span> <span class="keyword">implements</span> <span class="title">RequestInterceptor</span> </span>{</span><br><span class="line"> <span class="meta">@Override</span> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">apply</span><span class="params">(RequestTemplate template)</span> </span>{</span><br><span class="line"> template.header(<span class="string">"X-Forwarded-For"</span>, <span class="string">"origin.host.com"</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line">...</span><br><span class="line">Bank bank = Feign.builder()</span><br><span class="line"> .decoder(accountDecoder)</span><br><span class="line"> .requestInterceptor(<span class="keyword">new</span> ForwardedForInterceptor())</span><br><span class="line"> .target(Bank.class, <span class="string">"https://api.examplebank.com"</span>);</span><br></pre></td></tr></table></figure></p><p>或者，你可能需要实现Basic Auth，这里有一个内置的基础校验拦截器 <code>BasicAuthRequestInterceptor</code><br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">Bank bank = Feign.builder()</span><br><span class="line"> .decoder(accountDecoder)</span><br><span class="line"> .requestInterceptor(<span class="keyword">new</span> BasicAuthRequestInterceptor(username, password))</span><br><span class="line"> .target(Bank.class, <span class="string">"https://api.examplebank.com"</span>);</span><br></pre></td></tr></table></figure></p><h4 id="Custom-Param-Expansion"><a href="#Custom-Param-Expansion" class="headerlink" title="Custom @Param Expansion"></a>Custom @Param Expansion</h4><p>在使用 <code>@Param</code> 注解给模板中的参数设值的时候，默认的是使用的对象的 <code>toString()</code> 方法的值，通过声明 自定义的<code>Param.Expander</code>，用户可以控制其行为，比如说格式化 <code>Date</code> 类型的值:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 通过设置 @Param 的 expander 为 DateToMillis.class 可以定义Date类型的值</span></span><br><span class="line"><span class="meta">@RequestLine</span>(<span class="string">"GET /?since={date}"</span>)</span><br><span class="line"><span class="function">Result <span class="title">list</span><span class="params">(@Param(value = <span class="string">"date"</span>, expander = DateToMillis.class)</span> Date date)</span>;</span><br></pre></td></tr></table></figure></p><h4 id="Dynamic-Query-Parameters"><a href="#Dynamic-Query-Parameters" class="headerlink" title="Dynamic Query Parameters"></a>Dynamic Query Parameters</h4><p>动态查询参数支持，通过使用 <code>@QueryMap</code> 可以允许动态传入请求参数,如下:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestLine</span>(<span class="string">"GET /find"</span>)</span><br><span class="line"><span class="function">V <span class="title">find</span><span class="params">(@QueryMap Map<String, Object> queryMap)</span></span>;</span><br></pre></td></tr></table></figure></p><h4 id="Static-and-Default-Methods"><a href="#Static-and-Default-Methods" class="headerlink" title="Static and Default Methods"></a>Static and Default Methods</h4><p>如果你使用的是JDK 1.8+ 的话，那么你可以给接口设置统一的默认方法和静态方法,这个事JDK8的新特性，如下:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">GitHub</span> </span>{</span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"GET /repos/{owner}/{repo}/contributors"</span>)</span><br><span class="line"> <span class="function">List<Contributor> <span class="title">contributors</span><span class="params">(@Param(<span class="string">"owner"</span>)</span> String owner, @<span class="title">Param</span><span class="params">(<span class="string">"repo"</span>)</span> String repo)</span>;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"GET /users/{username}/repos?sort={sort}"</span>)</span><br><span class="line"> <span class="function">List<Repo> <span class="title">repos</span><span class="params">(@Param(<span class="string">"username"</span>)</span> String owner, @<span class="title">Param</span><span class="params">(<span class="string">"sort"</span>)</span> String sort)</span>;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">default</span> List<Repo> <span class="title">repos</span><span class="params">(String owner)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> repos(owner, <span class="string">"full_name"</span>);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * Lists all contributors for all repos owned by a user.</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="function"><span class="keyword">default</span> List<Contributor> <span class="title">contributors</span><span class="params">(String user)</span> </span>{</span><br><span class="line"> MergingContributorList contributors = <span class="keyword">new</span> MergingContributorList();</span><br><span class="line"> <span class="keyword">for</span>(Repo repo : <span class="keyword">this</span>.repos(owner)) {</span><br><span class="line"> contributors.addAll(<span class="keyword">this</span>.contributors(user, repo.getName()));</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> contributors.mergeResult();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">static</span> GitHub <span class="title">connect</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> Feign.builder()</span><br><span class="line"> .decoder(<span class="keyword">new</span> GsonDecoder())</span><br><span class="line"> .target(GitHub.class, <span class="string">"https://api.github.com"</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p>]]></content>
<summary type="html">
<p>英文原文请参考:<a href="https://github.com/OpenFeign/feign" target="_blank" rel="noopener">https://github.com/OpenFeign/feign</a><br>翻译参考:<a href="https://blog.csdn.net/u010862794/article/details/73649616" target="_blank" rel="noopener">https://blog.csdn.net/u010862794/article/details/73649616</a></p>
<h2 id="简介"><a href="#简介" class="headerlink" title="简介"></a>简介</h2><p>Feign是一款java的Restful客户端组件，Feign使得 Java HTTP 客户端编写更方便。Feign 灵感来源于<a href="https://github.com/square/retrofit" target="_blank" rel="noopener">Retrofit</a>, <a href="https://jax-rs-spec.java.net/nonav/2.0/apidocs/index.html" target="_blank" rel="noopener">JAXRS-2.0</a>和<a href="http://www.oracle.com/technetwork/articles/java/jsr356-1937161.html" target="_blank" rel="noopener">WebSocket</a>。Feign 最初是为了降低统一绑定<a href="https://github.com/Netflix/Denominator" target="_blank" rel="noopener">Denominator</a> 到 HTTP API 的复杂度，不区分是否支持 <a href="http://www.slideshare.net/adrianfcole/99problems" target="_blank" rel="noopener">ReSTfulness</a>。</p>
</summary>
<category term="spring" scheme="http://along101.site/categories/spring/"/>
<category term="java" scheme="http://along101.site/tags/java/"/>
<category term="rest" scheme="http://along101.site/tags/rest/"/>
<category term="feign" scheme="http://along101.site/tags/feign/"/>
</entry>
<entry>
<title>Feign源码解析</title>
<link href="http://along101.site/2018/06/13/feign-source-analysis/"/>
<id>http://along101.site/2018/06/13/feign-source-analysis/</id>
<published>2018-06-13T12:03:13.000Z</published>
<updated>2018-07-20T03:10:04.401Z</updated>
<content type="html"><![CDATA[<h2 id="Feign介绍"><a href="#Feign介绍" class="headerlink" title="Feign介绍"></a>Feign介绍</h2><p><a href="https://github.com/OpenFeign/feign/" target="_blank" rel="noopener">Feign</a>是一款java的Restful客户端组件，Feign使得 Java HTTP 客户端编写更方便。Feign 灵感来源于<a href="https://github.com/square/retrofit" target="_blank" rel="noopener">Retrofit</a>, <a href="https://jax-rs-spec.java.net/nonav/2.0/apidocs/index.html" target="_blank" rel="noopener">JAXRS-2.0</a>和<a href="http://www.oracle.com/technetwork/articles/java/jsr356-1937161.html" target="_blank" rel="noopener">WebSocket</a>。feign在github上有近3K个star，是一款相当优秀的开源组件，虽然相比Retrofit的近30K个star，逊色了太多，但是spring cloud集成了feign，使得feign在java生态中比Retrofit使用的更加广泛。</p><p>feign的基本原理是在接口方法上加注解，定义rest请求，构造出接口的动态代理对象，然后通过调用接口方法就可以发送http请求，并且自动解析http响应为方法返回值，极大的简化了客户端调用rest api的代码。官网的示例如下：</p><a id="more"></a><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">GitHub</span> </span>{</span><br><span class="line"> <span class="meta">@RequestLine</span>(<span class="string">"GET /repos/{owner}/{repo}/contributors"</span>)</span><br><span class="line"> <span class="function">List<Contributor> <span class="title">contributors</span><span class="params">(@Param(<span class="string">"owner"</span>)</span> String owner, @<span class="title">Param</span><span class="params">(<span class="string">"repo"</span>)</span> String repo)</span>;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="keyword">static</span> <span class="class"><span class="keyword">class</span> <span class="title">Contributor</span> </span>{</span><br><span class="line"> String login;</span><br><span class="line"> <span class="keyword">int</span> contributions;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String... args)</span> </span>{</span><br><span class="line"> GitHub github = Feign.builder()</span><br><span class="line"> .decoder(<span class="keyword">new</span> GsonDecoder())</span><br><span class="line"> .target(GitHub.class, <span class="string">"https://api.github.com"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// Fetch and print a list of the contributors to this library.</span></span><br><span class="line"> List<Contributor> contributors = github.contributors(<span class="string">"OpenFeign"</span>, <span class="string">"feign"</span>);</span><br><span class="line"> <span class="keyword">for</span> (Contributor contributor : contributors) {</span><br><span class="line"> System.out.println(contributor.login + <span class="string">" ("</span> + contributor.contributions + <span class="string">")"</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>feign使用教程请参考官网<a href="https://github.com/OpenFeign/feign/" target="_blank" rel="noopener">https://github.com/OpenFeign/feign/</a></p><p>本文主要是对feign源码进行分析，根据源码来理解feign的设计架构和内部实现技术。 </p><h2 id="Feign-build-构建接口动态代理"><a href="#Feign-build-构建接口动态代理" class="headerlink" title="Feign.build 构建接口动态代理"></a><code>Feign.build</code> 构建接口动态代理</h2><p>我们先来看看接口的动态代理是如何构建出来的，下图是主要接口和类的类图：</p><p><img src="/2018/06/13/feign-source-analysis/init1.png" alt=""></p><p>从上文中的示例可以看到，构建的接口动态代理对象是通过<code>Feign.builder()</code>生成<code>Feign.Builder</code>的构造者对象，然后设置相关的参数，再调用target方法构造的。<code>Feign.Builder</code>的参数包括：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><span class="comment">//拦截器，组装完RequestTemplate，发请求之前的拦截处理RequestTemplate</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">final</span> List<RequestInterceptor> requestInterceptors = <span class="keyword">new</span> ArrayList<RequestInterceptor>();</span><br><span class="line"><span class="comment">//日志级别</span></span><br><span class="line"> <span class="keyword">private</span> Logger.Level logLevel = Logger.Level.NONE;</span><br><span class="line"><span class="comment">//契约模型，默认为Contract.Default，用户创建MethodMetadata，用spring cloud就是扩展这个实现springMVC注解</span></span><br><span class="line"> <span class="keyword">private</span> Contract contract = <span class="keyword">new</span> Contract.Default();</span><br><span class="line"><span class="comment">//客户端，默认为Client.Default，可以扩展ApacheHttpClient，OKHttpClient，RibbonClient等</span></span><br><span class="line"> <span class="keyword">private</span> Client client = <span class="keyword">new</span> Client.Default(<span class="keyword">null</span>, <span class="keyword">null</span>);</span><br><span class="line"><span class="comment">//重试设置，默认不设置</span></span><br><span class="line"> <span class="keyword">private</span> Retryer retryer = <span class="keyword">new</span> Retryer.Default();</span><br><span class="line"><span class="comment">//日志，可以接入Slf4j</span></span><br><span class="line"> <span class="keyword">private</span> Logger logger = <span class="keyword">new</span> NoOpLogger();</span><br><span class="line"><span class="comment">//编码器，用于body的编码</span></span><br><span class="line"> <span class="keyword">private</span> Encoder encoder = <span class="keyword">new</span> Encoder.Default();</span><br><span class="line"><span class="comment">//解码器，用户response的解码</span></span><br><span class="line"> <span class="keyword">private</span> Decoder decoder = <span class="keyword">new</span> Decoder.Default();</span><br><span class="line"><span class="comment">//用@QueryMap注解的参数编码器</span></span><br><span class="line"> <span class="keyword">private</span> QueryMapEncoder queryMapEncoder = <span class="keyword">new</span> QueryMapEncoder.Default();</span><br><span class="line"><span class="comment">//请求错误解码器</span></span><br><span class="line"> <span class="keyword">private</span> ErrorDecoder errorDecoder = <span class="keyword">new</span> ErrorDecoder.Default();</span><br><span class="line"><span class="comment">//参数配置，主要是超时时间之类的</span></span><br><span class="line"> <span class="keyword">private</span> Options options = <span class="keyword">new</span> Options();</span><br><span class="line"><span class="comment">//动态代理工厂</span></span><br><span class="line"> <span class="keyword">private</span> InvocationHandlerFactory invocationHandlerFactory = <span class="keyword">new</span> InvocationHandlerFactory.Default();</span><br><span class="line"><span class="comment">//是否decode404</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">boolean</span> decode404;</span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">boolean</span> closeAfterDecode = <span class="keyword">true</span>;</span><br></pre></td></tr></table></figure><p>这块是一个典型的构造者模式，<code>target</code>方法内部先调用<code>build</code>方法新建一个<code>ReflectFeign</code>对象，然后调用<code>ReflectFeign</code>的<code>newInstance</code>方法创建动态代理，代码如下：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"> <span class="comment">//默认使用HardCodedTarget</span></span><br><span class="line"> <span class="keyword">public</span> <T> <span class="function">T <span class="title">target</span><span class="params">(Class<T> apiType, String url)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> target(<span class="keyword">new</span> HardCodedTarget<T>(apiType, url));</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> <T> <span class="function">T <span class="title">target</span><span class="params">(Target<T> target)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> build().newInstance(target);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> Feign <span class="title">build</span><span class="params">()</span> </span>{</span><br><span class="line"> SynchronousMethodHandler.Factory synchronousMethodHandlerFactory =</span><br><span class="line"> <span class="keyword">new</span> SynchronousMethodHandler.Factory(client, retryer, requestInterceptors, logger,</span><br><span class="line"> logLevel, decode404, closeAfterDecode);</span><br><span class="line"> ParseHandlersByName handlersByName =</span><br><span class="line"> <span class="keyword">new</span> ParseHandlersByName(contract, options, encoder, decoder, queryMapEncoder,</span><br><span class="line"> errorDecoder, synchronousMethodHandlerFactory);</span><br><span class="line"> <span class="comment">//handlersByName将所有参数进行封装，并提供解析接口方法的逻辑</span></span><br><span class="line"> <span class="comment">//invocationHandlerFactory是Builder的属性，默认值是InvocationHandlerFactory.Default,用创建java动态代理的InvocationHandler实现</span></span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> ReflectiveFeign(handlersByName, invocationHandlerFactory, queryMapEncoder);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p><code>ReflectiveFeign</code>构造函数有三个参数：</p><ul><li><code>ParseHandlersByName</code> 将builder所有参数进行封装，并提供解析接口方法的逻辑</li><li><code>InvocationHandlerFactory</code> java动态代理的<code>InvocationHandler</code>的工厂类，默认值是<code>InvocationHandlerFactory.Default</code></li><li><code>QueryMapEncoder</code> 接口参数注解<code>@QueryMap</code>时，参数的编码器</li></ul><p><code>ReflectiveFeign.newInstance</code>方法创建接口动态代理对象：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><span class="keyword">public</span> <T> <span class="function">T <span class="title">newInstance</span><span class="params">(Target<T> target)</span> </span>{</span><br><span class="line"> <span class="comment">//targetToHandlersByName是构造器传入的ParseHandlersByName对象，根据target对象生成MethodHandler映射</span></span><br><span class="line"> Map<String, MethodHandler> nameToHandler = targetToHandlersByName.apply(target);</span><br><span class="line"> Map<Method, MethodHandler> methodToHandler = <span class="keyword">new</span> LinkedHashMap<Method, MethodHandler>();</span><br><span class="line"> List<DefaultMethodHandler> defaultMethodHandlers = <span class="keyword">new</span> LinkedList<DefaultMethodHandler>();</span><br><span class="line"> <span class="comment">//遍历接口所有方法，构建Method->MethodHandler的映射</span></span><br><span class="line"> <span class="keyword">for</span> (Method method : target.type().getMethods()) {</span><br><span class="line"> <span class="keyword">if</span> (method.getDeclaringClass() == Object.class) {</span><br><span class="line"> <span class="keyword">continue</span>;</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span>(Util.isDefault(method)) {</span><br><span class="line"> <span class="comment">//接口default方法的Handler，这类方法直接调用</span></span><br><span class="line"> DefaultMethodHandler handler = <span class="keyword">new</span> DefaultMethodHandler(method);</span><br><span class="line"> defaultMethodHandlers.add(handler);</span><br><span class="line"> methodToHandler.put(method, handler);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> methodToHandler.put(method, nameToHandler.get(Feign.configKey(target.type(), method)));</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//这里factory是构造其中传入的，创建InvocationHandler</span></span><br><span class="line"> InvocationHandler handler = factory.create(target, methodToHandler);</span><br><span class="line"> <span class="comment">//java的动态代理</span></span><br><span class="line"> T proxy = (T) Proxy.newProxyInstance(target.type().getClassLoader(), <span class="keyword">new</span> Class<?>[]{target.type()}, handler);</span><br><span class="line"> <span class="comment">//将default方法直接绑定到动态代理上</span></span><br><span class="line"> <span class="keyword">for</span>(DefaultMethodHandler defaultMethodHandler : defaultMethodHandlers) {</span><br><span class="line"> defaultMethodHandler.bindTo(proxy);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> proxy;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>这段代码主要的逻辑是：</p><ol><li>创建<code>MethodHandler</code>的映射，这里创建的是实现类<code>SynchronousMethodHandler</code></li><li>通过<code>InvocationHandlerFatory</code>创建<code>InvocationHandler</code></li><li>绑定接口的<code>default</code>方法，通过<code>DefaultMethodHandler</code>绑定</li></ol><p>类图中已经画出，<code>SynchronousMethodHandler</code>和<code>DefaultMethodHandler</code>实现了<code>InvocationHandlerFactory.MethodHandler</code>接口，动态代理对象调用方法时，如果是<code>default</code>方法，会直接调用接口方法，因为这里将接口的<code>default</code>方法绑定到动态代理对象上了，其他方法根据方法签名找到<code>SynchronousMethodHandler</code>对象，调用其<code>invoke</code>方法。</p><h2 id="创建MethodHandler方法处理器"><a href="#创建MethodHandler方法处理器" class="headerlink" title="创建MethodHandler方法处理器"></a>创建MethodHandler方法处理器</h2><p><code>SynchronousMethodHandler</code>是feign组件的核心，接口方法调用转换为http请求和解析http响应都是通过<code>SynchronousMethodHandler</code>来执行的，相关类图如下：</p><p><img src="/2018/06/13/feign-source-analysis/init2.png" alt=""></p><p>创建<code>MethodHandler</code>实现类<code>SynchronousMethodHandler</code>的代码：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> Map<String, MethodHandler> <span class="title">apply</span><span class="params">(Target key)</span> </span>{</span><br><span class="line"> <span class="comment">//通过contract解析接口方法，生成MethodMetadata列表，默认的contract解析Feign自定义的http注解</span></span><br><span class="line"> List<MethodMetadata> metadata = contract.parseAndValidatateMetadata(key.type());</span><br><span class="line"> Map<String, MethodHandler> result = <span class="keyword">new</span> LinkedHashMap<String, MethodHandler>();</span><br><span class="line"> <span class="keyword">for</span> (MethodMetadata md : metadata) {</span><br><span class="line"> <span class="comment">//BuildTemplateByResolvingArgs实现RequestTemplate.Factory，RequestTemplate的工厂</span></span><br><span class="line"> BuildTemplateByResolvingArgs buildTemplate;</span><br><span class="line"> <span class="comment">//根据方法元数据，使用不同的RequestTemplate的工厂</span></span><br><span class="line"> <span class="keyword">if</span> (!md.formParams().isEmpty() && md.template().bodyTemplate() == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">//如果有formParam，并且bodyTemplate不为空，请求体为x-www-form-urlencoded格式</span></span><br><span class="line"> <span class="comment">//将会解析form参数，填充到bodyTemplate中</span></span><br><span class="line"> buildTemplate = <span class="keyword">new</span> BuildFormEncodedTemplateFromArgs(md, encoder, queryMapEncoder);</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (md.bodyIndex() != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">//如果包含请求体，将会用encoder编码请求体对象</span></span><br><span class="line"> buildTemplate = <span class="keyword">new</span> BuildEncodedTemplateFromArgs(md, encoder, queryMapEncoder);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">//默认的RequestTemplate的工厂，没有请求体，不需要编码器</span></span><br><span class="line"> buildTemplate = <span class="keyword">new</span> BuildTemplateByResolvingArgs(md, queryMapEncoder);</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//使用工厂SynchronousMethodHandler.Factory创建SynchronousMethodHandler</span></span><br><span class="line"> result.put(md.configKey(),</span><br><span class="line"> factory.create(key, md, buildTemplate, options, decoder, errorDecoder));</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>这段代码的逻辑是：</p><ol><li>通过<code>Contract</code>解析接口方法，生成<code>MethodMetadata</code>，默认的<code>Contract</code>解析Feign自定义的http注解</li><li>根据<code>MethodMetadata</code>方法元数据生成特定的<code>RequestTemplate</code>的工厂</li><li>使用<code>SynchronousMethodHandler.Factory</code>工厂创建<code>SynchronousMethodHandler</code><br>这里有两个工厂不要搞混淆了，<code>SynchronousMethodHandler</code>工厂和<code>RequestTemplate</code>工厂，<code>SynchronousMethodHandler</code>的属性包含<code>RequestTemplate</code>工厂</li></ol><h2 id="Contract解析接口方法生成MethodMetadata"><a href="#Contract解析接口方法生成MethodMetadata" class="headerlink" title="Contract解析接口方法生成MethodMetadata"></a><code>Contract</code>解析接口方法生成<code>MethodMetadata</code></h2><p>feign默认的解析器是<code>Contract.Default</code>继承了<code>Contract.BaseContract</code>，解析生成<code>MethodMetadata</code>方法入口：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br><span class="line">117</span><br><span class="line">118</span><br><span class="line">119</span><br><span class="line">120</span><br><span class="line">121</span><br><span class="line">122</span><br><span class="line">123</span><br><span class="line">124</span><br><span class="line">125</span><br><span class="line">126</span><br><span class="line">127</span><br><span class="line">128</span><br><span class="line">129</span><br><span class="line">130</span><br><span class="line">131</span><br><span class="line">132</span><br><span class="line">133</span><br><span class="line">134</span><br><span class="line">135</span><br><span class="line">136</span><br><span class="line">137</span><br><span class="line">138</span><br><span class="line">139</span><br><span class="line">140</span><br><span class="line">141</span><br><span class="line">142</span><br><span class="line">143</span><br><span class="line">144</span><br><span class="line">145</span><br><span class="line">146</span><br><span class="line">147</span><br><span class="line">148</span><br><span class="line">149</span><br><span class="line">150</span><br><span class="line">151</span><br><span class="line">152</span><br><span class="line">153</span><br><span class="line">154</span><br><span class="line">155</span><br><span class="line">156</span><br><span class="line">157</span><br><span class="line">158</span><br><span class="line">159</span><br><span class="line">160</span><br><span class="line">161</span><br><span class="line">162</span><br><span class="line">163</span><br><span class="line">164</span><br><span class="line">165</span><br><span class="line">166</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> List<MethodMetadata> <span class="title">parseAndValidatateMetadata</span><span class="params">(Class<?> targetType)</span> </span>{</span><br><span class="line"> 。。。</span><br><span class="line"> Map<String, MethodMetadata> result = <span class="keyword">new</span> LinkedHashMap<String, MethodMetadata>();</span><br><span class="line"> <span class="keyword">for</span> (Method method : targetType.getMethods()) {</span><br><span class="line"> 。。。</span><br><span class="line"> MethodMetadata metadata = parseAndValidateMetadata(targetType, method);</span><br><span class="line"> 。。。</span><br><span class="line"> result.put(metadata.configKey(), metadata);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> ArrayList<MethodMetadata>(result.values());</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">protected</span> MethodMetadata <span class="title">parseAndValidateMetadata</span><span class="params">(Class<?> targetType, Method method)</span> </span>{</span><br><span class="line"> MethodMetadata data = <span class="keyword">new</span> MethodMetadata();</span><br><span class="line"> data.returnType(Types.resolve(targetType, targetType, method.getGenericReturnType()));</span><br><span class="line"> data.configKey(Feign.configKey(targetType, method));</span><br><span class="line"></span><br><span class="line"> <span class="keyword">if</span>(targetType.getInterfaces().length == <span class="number">1</span>) {</span><br><span class="line"> processAnnotationOnClass(data, targetType.getInterfaces()[<span class="number">0</span>]);</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//处理Class上的注解</span></span><br><span class="line"> processAnnotationOnClass(data, targetType);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">for</span> (Annotation methodAnnotation : method.getAnnotations()) {</span><br><span class="line"> <span class="comment">//处理方法注解</span></span><br><span class="line"> processAnnotationOnMethod(data, methodAnnotation, method);</span><br><span class="line"> }</span><br><span class="line"> 。。。</span><br><span class="line"> Class<?>[] parameterTypes = method.getParameterTypes();</span><br><span class="line"> Type[] genericParameterTypes = method.getGenericParameterTypes();</span><br><span class="line"> <span class="comment">//方法参数注解</span></span><br><span class="line"> Annotation[][] parameterAnnotations = method.getParameterAnnotations();</span><br><span class="line"> <span class="keyword">int</span> count = parameterAnnotations.length;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < count; i++) {</span><br><span class="line"> <span class="keyword">boolean</span> isHttpAnnotation = <span class="keyword">false</span>;</span><br><span class="line"> <span class="keyword">if</span> (parameterAnnotations[i] != <span class="keyword">null</span>) {</span><br><span class="line"> isHttpAnnotation = processAnnotationsOnParameter(data, parameterAnnotations[i], i);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (parameterTypes[i] == URI.class) {</span><br><span class="line"> <span class="comment">//参数类型是URI，后面构造http请求时，使用该URI</span></span><br><span class="line"> data.urlIndex(i);</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (!isHttpAnnotation) {</span><br><span class="line"> <span class="comment">//如果没有被http注解，就是body参数</span></span><br><span class="line"> 。。。</span><br><span class="line"> data.bodyIndex(i);</span><br><span class="line"> data.bodyType(Types.resolve(targetType, targetType, genericParameterTypes[i]));</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">if</span> (data.headerMapIndex() != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">//@HeaderMap注解的参数必须是Map，key类型必须是String</span></span><br><span class="line"> checkMapString(<span class="string">"HeaderMap"</span>, parameterTypes[data.headerMapIndex()], genericParameterTypes[data.headerMapIndex()]);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">if</span> (data.queryMapIndex() != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">if</span> (Map.class.isAssignableFrom(parameterTypes[data.queryMapIndex()])) {</span><br><span class="line"> <span class="comment">//@QueryMap注解的参数如果是Map，key类型必须是String</span></span><br><span class="line"> checkMapKeys(<span class="string">"QueryMap"</span>, genericParameterTypes[data.queryMapIndex()]);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> data;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title">processAnnotationOnClass</span><span class="params">(MethodMetadata data, Class<?> targetType)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (targetType.isAnnotationPresent(Headers.class)) {</span><br><span class="line"> <span class="comment">//被Headers注解</span></span><br><span class="line"> String[] headersOnType = targetType.getAnnotation(Headers.class).value();</span><br><span class="line"> 。。。</span><br><span class="line"> <span class="comment">//header解析成map，加到MethodMetadata中</span></span><br><span class="line"> Map<String, Collection<String>> headers = toMap(headersOnType);</span><br><span class="line"> headers.putAll(data.template().headers());</span><br><span class="line"> data.template().headers(<span class="keyword">null</span>); <span class="comment">// to clear</span></span><br><span class="line"> data.template().headers(headers);</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title">processAnnotationOnMethod</span><span class="params">(MethodMetadata data, Annotation methodAnnotation,</span></span></span><br><span class="line"><span class="function"><span class="params"> Method method)</span> </span>{</span><br><span class="line"> Class<? extends Annotation> annotationType = methodAnnotation.annotationType();</span><br><span class="line"> <span class="keyword">if</span> (annotationType == RequestLine.class) {</span><br><span class="line"> <span class="comment">//@RequestLine注解</span></span><br><span class="line"> String requestLine = RequestLine.class.cast(methodAnnotation).value();</span><br><span class="line"> 。。。</span><br><span class="line"> <span class="keyword">if</span> (requestLine.indexOf(<span class="string">' '</span>) == -<span class="number">1</span>) {</span><br><span class="line"> 。。。</span><br><span class="line"> data.template().method(requestLine);</span><br><span class="line"> <span class="keyword">return</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//http请求方法</span></span><br><span class="line"> data.template().method(requestLine.substring(<span class="number">0</span>, requestLine.indexOf(<span class="string">' '</span>)));</span><br><span class="line"> <span class="keyword">if</span> (requestLine.indexOf(<span class="string">' '</span>) == requestLine.lastIndexOf(<span class="string">' '</span>)) {</span><br><span class="line"> <span class="comment">// no HTTP version is ok</span></span><br><span class="line"> data.template().append(requestLine.substring(requestLine.indexOf(<span class="string">' '</span>) + <span class="number">1</span>));</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">// skip HTTP version</span></span><br><span class="line"> data.template().append(</span><br><span class="line"> requestLine.substring(requestLine.indexOf(<span class="string">' '</span>) + <span class="number">1</span>, requestLine.lastIndexOf(<span class="string">' '</span>)));</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//将'%2F'反转为'/'</span></span><br><span class="line"> data.template().decodeSlash(RequestLine.class.cast(methodAnnotation).decodeSlash());</span><br><span class="line"> <span class="comment">//参数集合格式化方式，默认使用key=value0&key=value1</span></span><br><span class="line"> data.template().collectionFormat(RequestLine.class.cast(methodAnnotation).collectionFormat());</span><br><span class="line"></span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (annotationType == Body.class) {</span><br><span class="line"> <span class="comment">//@Body注解</span></span><br><span class="line"> String body = Body.class.cast(methodAnnotation).value();</span><br><span class="line"> 。。。</span><br><span class="line"> <span class="keyword">if</span> (body.indexOf(<span class="string">'{'</span>) == -<span class="number">1</span>) {</span><br><span class="line"> <span class="comment">//body中不存在{，直接传入body</span></span><br><span class="line"> data.template().body(body);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">//body中存在{，就是bodyTemplate方式</span></span><br><span class="line"> data.template().bodyTemplate(body);</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (annotationType == Headers.class) {</span><br><span class="line"> <span class="comment">//@Header注解</span></span><br><span class="line"> String[] headersOnMethod = Headers.class.cast(methodAnnotation).value();</span><br><span class="line"> 。。。</span><br><span class="line"> data.template().headers(toMap(headersOnMethod));</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//处理参数上的注解</span></span><br><span class="line"><span class="function"><span class="keyword">protected</span> <span class="keyword">boolean</span> <span class="title">processAnnotationsOnParameter</span><span class="params">(MethodMetadata data, Annotation[] annotations, <span class="keyword">int</span> paramIndex)</span> </span>{</span><br><span class="line"> <span class="keyword">boolean</span> isHttpAnnotation = <span class="keyword">false</span>;</span><br><span class="line"> <span class="keyword">for</span> (Annotation annotation : annotations) {</span><br><span class="line"> Class<? extends Annotation> annotationType = annotation.annotationType();</span><br><span class="line"> <span class="keyword">if</span> (annotationType == Param.class) {</span><br><span class="line"> <span class="comment">//@Param注解</span></span><br><span class="line"> Param paramAnnotation = (Param) annotation;</span><br><span class="line"> String name = paramAnnotation.value();</span><br><span class="line"> 。。。</span><br><span class="line"> <span class="comment">//增加到MethodMetadata中</span></span><br><span class="line"> nameParam(data, name, paramIndex);</span><br><span class="line"> <span class="comment">//@Param注解的expander参数，定义参数的解释器，默认是ToStringExpander，调用参数的toString方法</span></span><br><span class="line"> Class<? extends Param.Expander> expander = paramAnnotation.expander();</span><br><span class="line"> <span class="keyword">if</span> (expander != Param.ToStringExpander.class) {</span><br><span class="line"> data.indexToExpanderClass().put(paramIndex, expander);</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//参数是否已经urlEncoded，如果没有，会使用urlEncoded方式编码</span></span><br><span class="line"> data.indexToEncoded().put(paramIndex, paramAnnotation.encoded());</span><br><span class="line"> isHttpAnnotation = <span class="keyword">true</span>;</span><br><span class="line"> String varName = <span class="string">'{'</span> + name + <span class="string">'}'</span>;</span><br><span class="line"> <span class="keyword">if</span> (!data.template().url().contains(varName) &&</span><br><span class="line"> !searchMapValuesContainsSubstring(data.template().queries(), varName) &&</span><br><span class="line"> !searchMapValuesContainsSubstring(data.template().headers(), varName)) {</span><br><span class="line"> <span class="comment">//如果参数不在path里面，不在query里面，不在header里面，就设置到formParam中</span></span><br><span class="line"> data.formParams().add(name);</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (annotationType == QueryMap.class) {</span><br><span class="line"> <span class="comment">//@QueryMap注解，注解参数对象时，将该参数转换为http请求参数格式发送</span></span><br><span class="line"> 。。。</span><br><span class="line"> data.queryMapIndex(paramIndex);</span><br><span class="line"> data.queryMapEncoded(QueryMap.class.cast(annotation).encoded());</span><br><span class="line"> isHttpAnnotation = <span class="keyword">true</span>;</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (annotationType == HeaderMap.class) {</span><br><span class="line"> <span class="comment">//@HeaderMap注解，注解一个Map类型的参数，放入http header中发送</span></span><br><span class="line"> 。。。</span><br><span class="line"> data.headerMapIndex(paramIndex);</span><br><span class="line"> isHttpAnnotation = <span class="keyword">true</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> isHttpAnnotation;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>代码稍微有点多，但是逻辑很清晰，先处理类上的注解，再处理方法上注解，最后处理方法参数注解，把所有注解的情况都处理到就可以了。 </p><p>生成的<code>MethodMetadata</code>的结构如下：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">final</span> <span class="class"><span class="keyword">class</span> <span class="title">MethodMetadata</span> <span class="keyword">implements</span> <span class="title">Serializable</span> </span>{</span><br><span class="line"> <span class="comment">//标识方法的key，接口名加方法签名：GitHub#contributors(String,String)</span></span><br><span class="line"> <span class="keyword">private</span> String configKey;</span><br><span class="line"><span class="comment">//方法返回值类型</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">transient</span> Type returnType;</span><br><span class="line"><span class="comment">//uri参数的位置，方法中可以写个uri参数，发请求时直接使用这个参数</span></span><br><span class="line"> <span class="keyword">private</span> Integer urlIndex;</span><br><span class="line"><span class="comment">//body参数的位置，只能有一个未注解的参数为body，否则报错</span></span><br><span class="line"> <span class="keyword">private</span> Integer bodyIndex;</span><br><span class="line"><span class="comment">//headerMap参数的位置</span></span><br><span class="line"> <span class="keyword">private</span> Integer headerMapIndex;</span><br><span class="line"><span class="comment">//@QueryMap注解参数位置</span></span><br><span class="line"> <span class="keyword">private</span> Integer queryMapIndex;</span><br><span class="line"><span class="comment">//@QueryMap注解里面encode参数，是否已经urlEncode编码过了</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">boolean</span> queryMapEncoded;</span><br><span class="line"><span class="comment">//body的类型</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">transient</span> Type bodyType;</span><br><span class="line"><span class="comment">//RequestTemplate 原型</span></span><br><span class="line"> <span class="keyword">private</span> RequestTemplate template = <span class="keyword">new</span> RequestTemplate();</span><br><span class="line"><span class="comment">//form请求参数</span></span><br><span class="line"> <span class="keyword">private</span> List<String> formParams = <span class="keyword">new</span> ArrayList<String>();</span><br><span class="line"><span class="comment">//方法参数位置和名称的map</span></span><br><span class="line"> <span class="keyword">private</span> Map<Integer, Collection<String>> indexToName ;</span><br><span class="line"><span class="comment">//@Param中注解的expander方法，可以指定解析参数类</span></span><br><span class="line"> <span class="keyword">private</span> Map<Integer, Class<? extends Expander>> indexToExpanderClass ;</span><br><span class="line"><span class="comment">//参数是否被urlEncode编码过了，@Param中encoded方法</span></span><br><span class="line"> <span class="keyword">private</span> Map<Integer, Boolean> indexToEncoded ;</span><br><span class="line"><span class="comment">//自定义的Expander</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">transient</span> Map<Integer, Expander> indexToExpander;</span><br></pre></td></tr></table></figure><blockquote><p><code>Contract也</code>是feign的一个扩展点，一个优秀组件的架构通常是具有很强的扩展性，feign的架构本身很简单，设计的扩展点也很简单方便，所以受到spring的青睐，将其集成到spring cloud中。spring cloud就是通过<code>Contract</code>的扩展，实现使用springMVC的注解接入feign。feign自己还实现了使用jaxrs注解接入feign。</p></blockquote><h2 id="初始化总结"><a href="#初始化总结" class="headerlink" title="初始化总结"></a>初始化总结</h2><p>上文已经完成了feign初始化结构为动态代理的整个过程，简单的捋一遍：</p><ol><li>初始化<code>Feign.Builder</code>传入参数，构造<code>ReflectiveFeign</code></li><li><code>ReflectiveFeign</code>通过内部类<code>ParseHandlersByName</code>的<code>Contract</code>属性，解析接口生成<code>MethodMetadata</code></li><li><code>ParseHandlersByName</code>根据<code>MethodMetadata</code>生成<code>RequestTemplate</code>工厂</li><li><code>ParseHandlersByName</code>创建<code>SynchronousMethodHandler</code>，传入<code>MethodMetadata</code>、<code>RequestTemplate</code>工厂和<code>Feign.Builder</code>相关参数</li><li><code>ReflectiveFeign</code>创建<code>FeignInvocationHandler</code>，传入参数<code>SynchronousMethodHandler</code>，绑定<code>DefaultMethodHandler</code><br>6.<code>ReflectiveFeign</code>根据<code>FeignInvocationHandler</code>创建<code>Proxy</code></li></ol><p>关键的几个类是：</p><ul><li><code>ReflectiveFeign</code> 初始化入口</li><li><code>FeignInvocationHandler</code> 实现动态代理的<code>InvocHandler</code></li><li><code>SynchronousMethodHandler</code> 方法处理器，方法调用处理器</li><li><code>MethodMetadata</code> 方法元数据</li></ul><h2 id="接口调用"><a href="#接口调用" class="headerlink" title="接口调用"></a>接口调用</h2><p>为方便理解，分析完feign源码后，我将feign执行过程分成三层，如下图：</p><p><img src="/2018/06/13/feign-source-analysis/execute.png" alt=""></p><p>三层分别为：</p><ul><li>代理层 动态代理调用层</li><li>转换层 方法转http请求，解码http响应</li><li>网络层 http请求发送</li></ul><p>java动态代理接口方法调用，会调用到<code>InvocaHandler</code>的invoke方法，feign里面实现类是<code>FeignInvocationHandler</code>，invoke代码如下：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> Map<Method, MethodHandler> dispatch;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> Object <span class="title">invoke</span><span class="params">(Object proxy, Method method, Object[] args)</span> <span class="keyword">throws</span> Throwable </span>{</span><br><span class="line"> 。。。</span><br><span class="line"> <span class="keyword">return</span> dispatch.get(method).invoke(args);</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>根据方法找到<code>MethodHandler</code>，除接口的<code>default</code>方法外，找到的是<code>SynchronousMethodHandler</code>对象，然后调用<code>SynchronousMethodHandlerd.invoke</code>方法：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> Object <span class="title">invoke</span><span class="params">(Object[] argv)</span> <span class="keyword">throws</span> Throwable </span>{</span><br><span class="line"> <span class="comment">//buildTemplateFromArgs是RequestTemplate工程对象，根据方法参数创建RequestTemplate</span></span><br><span class="line"> RequestTemplate template = buildTemplateFromArgs.create(argv);</span><br><span class="line"> <span class="comment">//重试设置</span></span><br><span class="line"> Retryer retryer = <span class="keyword">this</span>.retryer.clone();</span><br><span class="line"> <span class="keyword">while</span> (<span class="keyword">true</span>) {</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//执行和解码</span></span><br><span class="line"> <span class="keyword">return</span> executeAndDecode(template);</span><br><span class="line"> } <span class="keyword">catch</span> (RetryableException e) {</span><br><span class="line"> retryer.continueOrPropagate(e);</span><br><span class="line"> 。。。</span><br><span class="line"> <span class="keyword">continue</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function">Object <span class="title">executeAndDecode</span><span class="params">(RequestTemplate template)</span> <span class="keyword">throws</span> Throwable </span>{</span><br><span class="line"> <span class="comment">//RequestTemplate转换为Request</span></span><br><span class="line"> Request request = targetRequest(template)</span><br><span class="line"> 。。。</span><br><span class="line"> Response response;</span><br><span class="line"> <span class="keyword">long</span> start = System.nanoTime();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> response = client.execute(request, options);</span><br><span class="line"> response.toBuilder().request(request).build();</span><br><span class="line"> } <span class="keyword">catch</span> (IOException e) {</span><br><span class="line"> 。。。</span><br><span class="line"> <span class="keyword">throw</span> errorExecuting(request, e);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">long</span> elapsedTime = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - start);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">boolean</span> shouldClose = <span class="keyword">true</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> 。。。</span><br><span class="line"> <span class="keyword">if</span> (Response.class == metadata.returnType()) {</span><br><span class="line"> <span class="comment">//如果接口方法返回的是Response类</span></span><br><span class="line"> <span class="keyword">if</span> (response.body() == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">//body为空，直接返回</span></span><br><span class="line"> <span class="keyword">return</span> response;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (response.body().length() == <span class="keyword">null</span> ||</span><br><span class="line"> response.body().length() > MAX_RESPONSE_BUFFER_SIZE) {</span><br><span class="line"> <span class="comment">//body不为空，且length>最大缓存值，返回response，但是不能关闭response</span></span><br><span class="line"> shouldClose = <span class="keyword">false</span>;</span><br><span class="line"> <span class="keyword">return</span> response;</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">// 读取body字节数组，返回response</span></span><br><span class="line"> <span class="keyword">byte</span>[] bodyData = Util.toByteArray(response.body().asInputStream());</span><br><span class="line"> <span class="keyword">return</span> response.toBuilder().body(bodyData).build();</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (response.status() >= <span class="number">200</span> && response.status() < <span class="number">300</span>) {</span><br><span class="line"> <span class="comment">//响应成功</span></span><br><span class="line"> <span class="keyword">if</span> (<span class="keyword">void</span>.class == metadata.returnType()) {</span><br><span class="line"> <span class="comment">//接口返回void</span></span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">null</span>;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">//解码response，直接调用decoder解码</span></span><br><span class="line"> Object result = decode(response);</span><br><span class="line"> shouldClose = closeAfterDecode;</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (decode404 && response.status() == <span class="number">404</span> && <span class="keyword">void</span>.class != metadata.returnType()) {</span><br><span class="line"> <span class="comment">//404解析</span></span><br><span class="line"> Object result = decode(response);</span><br><span class="line"> shouldClose = closeAfterDecode;</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">//其他返回码，使用errorDecoder解析，抛出异常</span></span><br><span class="line"> <span class="keyword">throw</span> errorDecoder.decode(metadata.configKey(), response);</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">catch</span> (IOException e) {</span><br><span class="line"> <span class="keyword">throw</span> errorReading(request, response, e);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> <span class="comment">//是否需要关闭response，根据Feign.Builder 参数设置是否要关闭流</span></span><br><span class="line"> <span class="keyword">if</span> (shouldClose) {</span><br><span class="line"> ensureClosed(response.body());</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>过程比较简单，生成<code>RquestTemplate</code> -> 转换为<code>Request</code> -> <code>client</code>发请求 -> <code>Decoder</code>解析<code>Response</code></p><h2 id="RquestTemplate构建过程"><a href="#RquestTemplate构建过程" class="headerlink" title="RquestTemplate构建过程"></a><code>RquestTemplate</code>构建过程</h2><p>先看看<code>RequestTemplate</code>的结构：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="keyword">long</span> serialVersionUID = <span class="number">1L</span>;</span><br><span class="line"><span class="comment">//请求参数 ?后面的name=value</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">final</span> Map<String, Collection<String>> queries ;</span><br><span class="line"><span class="comment">//请求头</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">final</span> Map<String, Collection<String>> headers ;</span><br><span class="line"><span class="comment">//请求方法 GET/POST等</span></span><br><span class="line"> <span class="keyword">private</span> String method;</span><br><span class="line"><span class="comment">//请求路径</span></span><br><span class="line"> <span class="keyword">private</span> StringBuilder url = <span class="keyword">new</span> StringBuilder();</span><br><span class="line"><span class="comment">//字符集</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">transient</span> Charset charset;</span><br><span class="line"><span class="comment">//请求体</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">byte</span>[] body;</span><br><span class="line"><span class="comment">//@Body("%7B\"user_name\": \"{user_name}\", \"password\": \"{password}\"%7D")注解的模板</span></span><br><span class="line"> <span class="keyword">private</span> String bodyTemplate;</span><br><span class="line"><span class="comment">//是否decode削减，将"%2F"反转为"/"</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">boolean</span> decodeSlash = <span class="keyword">true</span>;</span><br><span class="line"><span class="comment">//集合格式化，分隔符</span></span><br><span class="line"> <span class="keyword">private</span> CollectionFormat collectionFormat = CollectionFormat.EXPLODED;</span><br></pre></td></tr></table></figure></p><p>在<code>SynchronousMethodHandler.invoke</code>方法中生成<code>RequestTemplate</code><br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//buildTemplateFromArgs是RequestTemplate.Factory实现类</span></span><br><span class="line">RequestTemplate template = buildTemplateFromArgs.create(argv);</span><br></pre></td></tr></table></figure></p><p><code>RequestTemplate.Factory</code>有三个实现类：</p><ul><li><code>BuildTemplateByResolvingArgs</code> <code>RequestTemplate</code>工厂</li><li><code>BuildEncodedTemplateFromArgs</code> <code>BuildTemplateByResolvingArgs</code>的子类 重载<code>resolve</code>方法，解析form表单请求</li><li><code>BuildFormEncodedTemplateFromArgs</code> <code>BuildTemplateByResolvingArgs</code>的子类，重载<code>resolve</code>方法，解析body请求</li></ul><p><code>BuildTemplateByResolvingArgs</code>创建<code>RequestTemplate</code>的<code>create</code>方法：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//BuildTemplateByResolvingArgs实现RequestTemplate.Factory的方法</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> RequestTemplate <span class="title">create</span><span class="params">(Object[] argv)</span> </span>{</span><br><span class="line"> RequestTemplate mutable = <span class="keyword">new</span> RequestTemplate(metadata.template());</span><br><span class="line"> <span class="keyword">if</span> (metadata.urlIndex() != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">//插入接口方法参数中的URI</span></span><br><span class="line"> <span class="keyword">int</span> urlIndex = metadata.urlIndex();</span><br><span class="line"> mutable.insert(<span class="number">0</span>, String.valueOf(argv[urlIndex]));</span><br><span class="line"> }</span><br><span class="line"> Map<String, Object> varBuilder = <span class="keyword">new</span> LinkedHashMap<String, Object>();</span><br><span class="line"> <span class="comment">//方法参数位置和请求定义的参数名称的map</span></span><br><span class="line"> <span class="keyword">for</span> (Entry<Integer, Collection<String>> entry : metadata.indexToName().entrySet()) {</span><br><span class="line"> <span class="comment">//将方法参数值和定义的请求参数进行映射，varBuilder</span></span><br><span class="line"> <span class="keyword">int</span> i = entry.getKey();</span><br><span class="line"> Object value = argv[entry.getKey()];</span><br><span class="line"> <span class="keyword">if</span> (value != <span class="keyword">null</span>) { <span class="comment">// Null values are skipped.</span></span><br><span class="line"> <span class="keyword">if</span> (indexToExpander.containsKey(i)) {</span><br><span class="line"> value = expandElements(indexToExpander.get(i), value);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">for</span> (String name : entry.getValue()) {</span><br><span class="line"> varBuilder.put(name, value);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//解析RequestTemplate</span></span><br><span class="line"> RequestTemplate template = resolve(argv, mutable, varBuilder);</span><br><span class="line"> <span class="comment">//解析queryMap，这块代码有些奇怪，为什么单独把queryMap放在这里解析，而不是在resolve方法中，或者在RequestTemplate中</span></span><br><span class="line"> <span class="keyword">if</span> (metadata.queryMapIndex() != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">// add query map parameters after initial resolve so that they take</span></span><br><span class="line"> <span class="comment">// precedence over any predefined values</span></span><br><span class="line"> Object value = argv[metadata.queryMapIndex()];</span><br><span class="line"> Map<String, Object> queryMap = toQueryMap(value);</span><br><span class="line"> template = addQueryMapQueryParameters(queryMap, template);</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//解析headerMap定义的参数</span></span><br><span class="line"> <span class="keyword">if</span> (metadata.headerMapIndex() != <span class="keyword">null</span>) {</span><br><span class="line"> template = addHeaderMapHeaders((Map<String, Object>) argv[metadata.headerMapIndex()], template);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> template;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//BuildTemplateByResolvingArgs</span></span><br><span class="line"><span class="function"><span class="keyword">protected</span> RequestTemplate <span class="title">resolve</span><span class="params">(Object[] argv, RequestTemplate mutable,</span></span></span><br><span class="line"><span class="function"><span class="params"> Map<String, Object> variables)</span> </span>{</span><br><span class="line"> <span class="comment">// 根据需要进行urlEncode参数</span></span><br><span class="line"> Map<String, Boolean> variableToEncoded = <span class="keyword">new</span> LinkedHashMap<String, Boolean>();</span><br><span class="line"> <span class="keyword">for</span> (Entry<Integer, Boolean> entry : metadata.indexToEncoded().entrySet()) {</span><br><span class="line"> Collection<String> names = metadata.indexToName().get(entry.getKey());</span><br><span class="line"> <span class="keyword">for</span> (String name : names) {</span><br><span class="line"> variableToEncoded.put(name, entry.getValue());</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//解析参数</span></span><br><span class="line"> <span class="keyword">return</span> mutable.resolve(variables, variableToEncoded);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//BuildEncodedTemplateFromArgs</span></span><br><span class="line"><span class="function"><span class="keyword">protected</span> RequestTemplate <span class="title">resolve</span><span class="params">(Object[] argv, RequestTemplate mutable,</span></span></span><br><span class="line"><span class="function"><span class="params"> Map<String, Object> variables)</span> </span>{</span><br><span class="line"> Object body = argv[metadata.bodyIndex()];</span><br><span class="line"> checkArgument(body != <span class="keyword">null</span>, <span class="string">"Body parameter %s was null"</span>, metadata.bodyIndex());</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//编码并设置RequestTemplate的body</span></span><br><span class="line"> encoder.encode(body, metadata.bodyType(), mutable);</span><br><span class="line"> } <span class="keyword">catch</span> (EncodeException e) {</span><br><span class="line"> <span class="keyword">throw</span> e;</span><br><span class="line"> } <span class="keyword">catch</span> (RuntimeException e) {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> EncodeException(e.getMessage(), e);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">super</span>.resolve(argv, mutable, variables);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//BuildFormEncodedTemplateFromArgs</span></span><br><span class="line"><span class="function"><span class="keyword">protected</span> RequestTemplate <span class="title">resolve</span><span class="params">(Object[] argv, RequestTemplate mutable,</span></span></span><br><span class="line"><span class="function"><span class="params"> Map<String, Object> variables)</span> </span>{</span><br><span class="line"> <span class="comment">//构造form参数，为HashMap</span></span><br><span class="line"> Map<String, Object> formVariables = <span class="keyword">new</span> LinkedHashMap<String, Object>();</span><br><span class="line"> <span class="keyword">for</span> (Entry<String, Object> entry : variables.entrySet()) {</span><br><span class="line"> <span class="keyword">if</span> (metadata.formParams().contains(entry.getKey())) {</span><br><span class="line"> formVariables.put(entry.getKey(), entry.getValue());</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//编码并设置RequestTemplate的body，</span></span><br><span class="line"> encoder.encode(formVariables, Encoder.MAP_STRING_WILDCARD, mutable);</span><br><span class="line"> } <span class="keyword">catch</span> (EncodeException e) {</span><br><span class="line"> <span class="keyword">throw</span> e;</span><br><span class="line"> } <span class="keyword">catch</span> (RuntimeException e) {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> EncodeException(e.getMessage(), e);</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//调用父类的resolve</span></span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">super</span>.resolve(argv, mutable, variables);</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p><code>RequestTemplate</code>解析参数的方法：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//RequestTemplate解析参数的方法</span></span><br><span class="line"><span class="function">RequestTemplate <span class="title">resolve</span><span class="params">(Map<String, ?> unencoded, Map<String, Boolean> alreadyEncoded)</span> </span>{</span><br><span class="line"> <span class="comment">//替换请求Query中的参数</span></span><br><span class="line"> replaceQueryValues(unencoded, alreadyEncoded);</span><br><span class="line"> Map<String, String> encoded = <span class="keyword">new</span> LinkedHashMap<String, String>();</span><br><span class="line"> <span class="keyword">for</span> (Entry<String, ?> entry : unencoded.entrySet()) {</span><br><span class="line"> <span class="keyword">final</span> String key = entry.getKey();</span><br><span class="line"> <span class="keyword">final</span> Object objectValue = entry.getValue();</span><br><span class="line"> String encodedValue = encodeValueIfNotEncoded(key, objectValue, alreadyEncoded);</span><br><span class="line"> encoded.put(key, encodedValue);</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//解析Url，替换path中的参数</span></span><br><span class="line"> String resolvedUrl = expand(url.toString(), encoded).replace(<span class="string">"+"</span>, <span class="string">"%20"</span>);</span><br><span class="line"> <span class="keyword">if</span> (decodeSlash) {</span><br><span class="line"> resolvedUrl = resolvedUrl.replace(<span class="string">"%2F"</span>, <span class="string">"/"</span>);</span><br><span class="line"> }</span><br><span class="line"> url = <span class="keyword">new</span> StringBuilder(resolvedUrl);</span><br><span class="line"> <span class="comment">//解析http请求的header</span></span><br><span class="line"> Map<String, Collection<String>> resolvedHeaders = <span class="keyword">new</span> LinkedHashMap<String, Collection<String>>();</span><br><span class="line"> <span class="keyword">for</span> (String field : headers.keySet()) {</span><br><span class="line"> Collection<String> resolvedValues = <span class="keyword">new</span> ArrayList<String>();</span><br><span class="line"> <span class="keyword">for</span> (String value : valuesOrEmpty(headers, field)) {</span><br><span class="line"> String resolved = expand(value, unencoded);</span><br><span class="line"> resolvedValues.add(resolved);</span><br><span class="line"> }</span><br><span class="line"> resolvedHeaders.put(field, resolvedValues);</span><br><span class="line"> }</span><br><span class="line"> headers.clear();</span><br><span class="line"> headers.putAll(resolvedHeaders);</span><br><span class="line"> <span class="comment">//处理bodyTemplate</span></span><br><span class="line"> <span class="keyword">if</span> (bodyTemplate != <span class="keyword">null</span>) {</span><br><span class="line"> body(urlDecode(expand(bodyTemplate, encoded)));</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">this</span>;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//工具方法，将含有{varName}的字符串模板中的变量名用变量值替换</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> String <span class="title">expand</span><span class="params">(String template, Map<String, ?> variables)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (checkNotNull(template, <span class="string">"template"</span>).length() < <span class="number">3</span>) {</span><br><span class="line"> <span class="keyword">return</span> template;</span><br><span class="line"> }</span><br><span class="line"> checkNotNull(variables, <span class="string">"variables for %s"</span>, template);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">boolean</span> inVar = <span class="keyword">false</span>;</span><br><span class="line"> StringBuilder var = <span class="keyword">new</span> StringBuilder();</span><br><span class="line"> StringBuilder builder = <span class="keyword">new</span> StringBuilder();</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">char</span> c : template.toCharArray()) {</span><br><span class="line"> <span class="keyword">switch</span> (c) {</span><br><span class="line"> <span class="keyword">case</span> <span class="string">'{'</span>:</span><br><span class="line"> <span class="keyword">if</span> (inVar) {</span><br><span class="line"> <span class="comment">// '{{' is an escape: write the brace and don't interpret as a variable</span></span><br><span class="line"> builder.append(<span class="string">"{"</span>);</span><br><span class="line"> inVar = <span class="keyword">false</span>;</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> }</span><br><span class="line"> inVar = <span class="keyword">true</span>;</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> <span class="keyword">case</span> <span class="string">'}'</span>:</span><br><span class="line"> <span class="keyword">if</span> (!inVar) { <span class="comment">// then write the brace literally</span></span><br><span class="line"> builder.append(<span class="string">'}'</span>);</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> }</span><br><span class="line"> inVar = <span class="keyword">false</span>;</span><br><span class="line"> String key = var.toString();</span><br><span class="line"> Object value = variables.get(var.toString());</span><br><span class="line"> <span class="keyword">if</span> (value != <span class="keyword">null</span>) {</span><br><span class="line"> builder.append(value);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> builder.append(<span class="string">'{'</span>).append(key).append(<span class="string">'}'</span>);</span><br><span class="line"> }</span><br><span class="line"> var = <span class="keyword">new</span> StringBuilder();</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> <span class="keyword">default</span>:</span><br><span class="line"> <span class="keyword">if</span> (inVar) {</span><br><span class="line"> var.append(c);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> builder.append(c);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> builder.toString();</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><h2 id="RquestTemplate转换Request"><a href="#RquestTemplate转换Request" class="headerlink" title="RquestTemplate转换Request"></a><code>RquestTemplate</code>转换<code>Request</code></h2><p>先来看看<code>Request</code>的结构，完整的http请求信息的定义：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> String method;</span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> String url;</span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> Map<String, Collection<String>> headers;</span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> <span class="keyword">byte</span>[] body;</span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> Charset charset;</span><br></pre></td></tr></table></figure><p><code>SynchronousMethodHandler</code>的<code>targetRequest</code>方法将<code>RequestTemplate</code>转换为<code>Request</code><br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="function">Request <span class="title">targetRequest</span><span class="params">(RequestTemplate template)</span> </span>{</span><br><span class="line"> <span class="comment">//先应用所用拦截器，拦截器是在Feign.Builder中传入的，拦截器可以修改RequestTemplate信息</span></span><br><span class="line"> <span class="keyword">for</span> (RequestInterceptor interceptor : requestInterceptors) {</span><br><span class="line"> interceptor.apply(template);</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//调用Target的apply方法，默认Target是HardCodedTarget</span></span><br><span class="line"> <span class="keyword">return</span> target.apply(<span class="keyword">new</span> RequestTemplate(template));</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>这块先应用所有拦截器，然后target的<code>apply</code>方法。拦截器和target都是扩展点，拦截器可以在构造好<code>RequestTemplate</code>后和发请求前修改请求信息，target默认使用<code>HardCodedTarget</code>直接发请求，feign还提供了<code>LoadBalancingTarget</code>，适配Ribbon来发请求，实现客户端的负载均衡。 </p><p>创建过程：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"> <span class="comment">//HardCodedTarget的apply方法</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> Request <span class="title">apply</span><span class="params">(RequestTemplate input)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (input.url().indexOf(<span class="string">"http"</span>) != <span class="number">0</span>) {</span><br><span class="line"> input.insert(<span class="number">0</span>, url());</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//调用RequestTemplate的request方法</span></span><br><span class="line"> <span class="keyword">return</span> input.request();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">//RequestTemplate的request方法</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> Request <span class="title">request</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="comment">//安全拷贝所有header</span></span><br><span class="line"> Map<String, Collection<String>> safeCopy = <span class="keyword">new</span> LinkedHashMap<String, Collection<String>>();</span><br><span class="line"> safeCopy.putAll(headers);</span><br><span class="line"> <span class="comment">//调用Request的create静态方法</span></span><br><span class="line"> <span class="keyword">return</span> Request.create(</span><br><span class="line"> method, url + queryLine(),</span><br><span class="line"> Collections.unmodifiableMap(safeCopy),</span><br><span class="line"> body, charset</span><br><span class="line"> );</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//Request的create方法</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> Request <span class="title">create</span><span class="params">(String method, String url, Map<String, Collection<String>> headers,</span></span></span><br><span class="line"><span class="function"><span class="params"> <span class="keyword">byte</span>[] body, Charset charset)</span> </span>{</span><br><span class="line"> <span class="comment">//new 对象</span></span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> Request(method, url, headers, body, charset);</span><br><span class="line"> }</span><br></pre></td></tr></table></figure></p><p>从代码上可以看到，<code>RequestTemplate</code>基本上直接转为<code>Request</code>，没有做什么逻辑操作。对比下<code>LoadBalancingTarget</code>：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> Request <span class="title">apply</span><span class="params">(RequestTemplate input)</span> </span>{</span><br><span class="line"> <span class="comment">//选取一个Server，lb是Ribbon的AbstractLoadBalancer类</span></span><br><span class="line"> Server currentServer = lb.chooseServer(<span class="keyword">null</span>);</span><br><span class="line"> <span class="comment">//生成url</span></span><br><span class="line"> String url = format(<span class="string">"%s://%s%s"</span>, scheme, currentServer.getHostPort(), path);</span><br><span class="line"> input.insert(<span class="number">0</span>, url);</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//生成Request</span></span><br><span class="line"> <span class="keyword">return</span> input.request();</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> lb.getLoadBalancerStats().incrementNumRequests(currentServer);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>可以看到，非常简单的几行代码，只要修改请求的url就能实现客户端负载均衡。</p><h2 id="http请求发送"><a href="#http请求发送" class="headerlink" title="http请求发送"></a>http请求发送</h2><p><code>SynchronousMethodHandler</code>中构造好<code>Request</code>后，直接调用client的<code>execute</code>方法发送请求：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">response = client.execute(request, options);</span><br></pre></td></tr></table></figure><p>client是一个<code>Client</code>接口，默认实现类是<code>Client.Default</code>，使用java api中的<code>HttpURLConnection</code>发送http请求。feign还实现了：</p><ul><li><code>ApacheHttpClient</code></li><li><code>OkHttpClient</code></li><li><code>RibbonClient</code><br>使用<code>RibbonClient</code>跟使用<code>LoadBalancingTarget</code>作用都是实现客户端负载均衡，<code>RibbonClient</code>实现稍微复杂些。</li></ul><h2 id="接口调用过程总结"><a href="#接口调用过程总结" class="headerlink" title="接口调用过程总结"></a>接口调用过程总结</h2><p>我们再将接口调用过程捋一遍：</p><p>1、接口的动态代理<code>Proxy</code>调用接口方法会执行的<code>FeignInvocationHandler</code><br>2、<code>FeignInvocationHandler</code>通过方法签名在属性<code>Map<Method, MethodHandler> dispatch</code>中找到<code>SynchronousMethodHandler</code>，调用<code>invoke</code>方法<br>3、<code>SynchronousMethodHandler</code>的<code>invoke</code>方法根据传入的方法参数，通过自身属性工厂对象<code>RequestTemplate.Factory</code>创建<code>RequestTemplate</code>，工厂里面会用根据需要进行<code>Encode</code><br>4、<code>SynchronousMethodHandler</code>遍历自身属性<code>RequestInterceptor</code>列表，对<code>RequestTemplate</code>进行改造<br>4、<code>SynchronousMethodHandler</code>调用自身<code>Target</code>属性的<code>apply</code>方法，将<code>RequestTemplate</code>转换为<code>Request</code>对象<br>5、<code>SynchronousMethodHandler</code>调用自身<code>Client</code>的<code>execute</code>方法，传入<code>Request</code>对象<br>6、<code>Client</code>将<code>Request</code>转换为<code>http</code>请求，发送后将http响应转换为<code>Response</code>对象<br>7、<code>SynchronousMethodHandler</code>调用<code>Decoder</code>的方法对<code>Response</code>对象解码后返回<br>8、返回的对象最后返回到<code>Proxy</code></p><p>时序图如下：<br><img src="/2018/06/13/feign-source-analysis/execute-sequence.png" alt=""></p><h2 id="feign扩展点总结"><a href="#feign扩展点总结" class="headerlink" title="feign扩展点总结"></a>feign扩展点总结</h2><p>前文分析源代码时，已经提到了feign的扩展点，最后我们再将feign的主要扩展点进行总结一下：</p><ul><li><p><code>Contract</code> 契约<br><code>Contract</code>的作用是解析接口方法，生成Rest定义。feign默认使用自己的定义的注解，还提供了</p><ul><li><code>JAXRSContract</code> javax.ws.rs注解接口实现<br><code>SpringContract</code>是spring cloud提供SpringMVC注解实现方式。</li></ul></li><li><p><code>InvocationHandler</code> 动态代理handler<br>通过<code>InvocationHandlerFactory</code>注入到<code>Feign.Builder</code>中，feign提供了Hystrix的扩展，实现Hystrix接入</p></li><li><p><code>Encoder</code> 请求body编码器<br>feign已经提供扩展包含：</p><ul><li>默认编码器，只能处理String和byte[]</li><li>json编码器<code>GsonEncoder</code>、<code>JacksonEncoder</code></li><li>XML编码器<code>JAXBEncoder</code></li></ul></li><li><p><code>Decoder</code> http响应解码器<br>最基本的有：</p><ul><li>json解码器 <code>GsonDecoder</code>、<code>JacksonDecoder</code></li><li>XML解码器 <code>JAXBDecoder</code></li><li>Stream流解码器 <code>StreamDecoder</code></li></ul></li><li><p><code>Target</code> 请求转换器<br>feign提供的实现有：</p><ul><li><code>HardCodedTarget</code> 默认<code>Target</code>，不做任何处理。</li><li><code>LoadBalancingTarget</code> 使用Ribbon进行客户端路由</li></ul></li><li><p><code>Client</code> 发送http请求的客户端<br>feign提供的<code>Client</code>实现有：</p><ul><li><code>Client.Default</code> 默认实现，使用java api的<code>HttpClientConnection</code>发送http请求</li><li><code>ApacheHttpClient</code> 使用apache的Http客户端发送请求</li><li><code>OkHttpClient</code> 使用OKHttp客户端发送请求</li><li><code>RibbonClient</code> 使用Ribbon进行客户端路由</li></ul></li><li><p><code>RequestInterceptor</code> 请求拦截器<br>调用客户端发请求前，修改<code>RequestTemplate</code>，比如为所有请求添加Header就可以用拦截器实现。</p></li><li><p><code>Retryer</code> 重试策略<br>默认的策略是<code>Retryer.Default</code>，包含<code>3</code>个参数：间隔、最大间隔和重试次数，第一次失败重试前会sleep输入的间隔时间的，后面每次重试sleep时间是前一次的<code>1.5</code>倍，超过最大时间或者最大重试次数就失败</p></li></ul>]]></content>
<summary type="html">
<h2 id="Feign介绍"><a href="#Feign介绍" class="headerlink" title="Feign介绍"></a>Feign介绍</h2><p><a href="https://github.com/OpenFeign/feign/" target="_blank" rel="noopener">Feign</a>是一款java的Restful客户端组件，Feign使得 Java HTTP 客户端编写更方便。Feign 灵感来源于<a href="https://github.com/square/retrofit" target="_blank" rel="noopener">Retrofit</a>, <a href="https://jax-rs-spec.java.net/nonav/2.0/apidocs/index.html" target="_blank" rel="noopener">JAXRS-2.0</a>和<a href="http://www.oracle.com/technetwork/articles/java/jsr356-1937161.html" target="_blank" rel="noopener">WebSocket</a>。feign在github上有近3K个star，是一款相当优秀的开源组件，虽然相比Retrofit的近30K个star，逊色了太多，但是spring cloud集成了feign，使得feign在java生态中比Retrofit使用的更加广泛。</p>
<p>feign的基本原理是在接口方法上加注解，定义rest请求，构造出接口的动态代理对象，然后通过调用接口方法就可以发送http请求，并且自动解析http响应为方法返回值，极大的简化了客户端调用rest api的代码。官网的示例如下：</p>
</summary>
<category term="spring" scheme="http://along101.site/categories/spring/"/>
<category term="java" scheme="http://along101.site/tags/java/"/>
<category term="rest" scheme="http://along101.site/tags/rest/"/>
<category term="feign" scheme="http://along101.site/tags/feign/"/>
</entry>
<entry>
<title>微服务动态配置组件netflix archaius</title>
<link href="http://along101.site/2018/05/14/netflix-archaius/"/>
<id>http://along101.site/2018/05/14/netflix-archaius/</id>
<published>2018-05-14T12:03:13.000Z</published>
<updated>2018-07-20T03:10:04.409Z</updated>
<content type="html"><![CDATA[<h1 id="archaius介绍"><a href="#archaius介绍" class="headerlink" title="archaius介绍"></a>archaius介绍</h1><p>archaius是Netflix公司开源项目之一，基于java的配置管理类库，主要用于多配置存储的动态获取。主要功能是对apache common configuration类库的扩展。在云平台开发中可以将其用作分布式配置管理依赖构件。同时，它有如下一些特性：</p><ul><li>动态获取属性</li><li>高效和线程安全的配置操作</li><li>配置改变时提供回调机制</li><li>可以通过jmx操作配置</li><li>复合配置</li></ul><a id="more"></a><p>官网给出的结构图：<br><img src="/2018/05/14/netflix-archaius/archaius.png" alt=""></p><h1 id="适用场景"><a href="#适用场景" class="headerlink" title="适用场景"></a>适用场景</h1><p>对于传统的单体应用，properties等配置文件可以解决配置问题，同时也可以通过maven profile配置来区别各个环境，但在一个几百上千节点的的微服务生态中，如何把每个微服务的配置文件都进行更新，并且很多时候还需要重启服务，是一件无法忍受的事情。<br>对于微服务架构而言，一个通用的配置中心是必不可少的。zookeeper、consul、etcd都可以作为集中的配置中心，但是他们的客户端api不是为配置而编写的，使用到配置场景时，会显得非常的臃肿，Archaius可以与这些配置中心结合，它提供的动态配置api，使用起来非常简单方便。<br>spring cloud的spring-cloud-netflix-core组件中集成了archaius，hystrix使用archaius动态修改各commandKey对应的参数（并发数和超时时间），用简单优雅的代码实现不重启生效配置项。</p><h1 id="快速入门"><a href="#快速入门" class="headerlink" title="快速入门"></a>快速入门</h1><p>在maven工程中加入依赖的配置：<br><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>com.netflix.archaius<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>archaius-core<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>0.7.4<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">dependency</span>></span></span><br></pre></td></tr></table></figure></p><p>archaius已经发展到2.x版本，但是spring cloud集成的还是0.7.X </p><p>编写示例代码：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Main</span> </span>{</span><br><span class="line"> <span class="comment">//获取一个Long型的动态配置项，默认值是1000。</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> DynamicLongProperty timeToWait =</span><br><span class="line"> DynamicPropertyFactory.getInstance().getLongProperty(<span class="string">"lock.waitTime"</span>, <span class="number">1000</span>);</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> <span class="comment">//设置回调</span></span><br><span class="line"> timeToWait.addCallback(() -> {</span><br><span class="line"> System.out.println(<span class="string">"timeToWait callback, new value: "</span> + timeToWait.get());</span><br><span class="line"> });</span><br><span class="line"> <span class="comment">//每秒将timeToWait动态配置值打印到控制台，timeToWait.get()会动态的获取最新的配置</span></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < <span class="number">100000</span>; i++) {</span><br><span class="line"> Thread.sleep(<span class="number">1000</span>);</span><br><span class="line"> System.out.println(<span class="string">"timeToWait: "</span> + timeToWait.get());</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>archaius默认读取classpath下的config.properties，所以在resources目录下增加config.properties文件，文件中增加配置：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">lock.waitTime=4</span><br></pre></td></tr></table></figure><p>然后运行Main，会在控制台打印：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">timeToWait: 4</span><br><span class="line">timeToWait: 4</span><br><span class="line">timeToWait: 4</span><br><span class="line">。。。</span><br></pre></td></tr></table></figure><p>让main继续运行，修改config.properties配置文件内容：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">lock.waitTime=5</span><br></pre></td></tr></table></figure></p><p>重新编译工程，等待1分钟左右，控制台会打印：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">timeToWait: 4</span><br><span class="line">timeToWait callback, new value: 5</span><br><span class="line">timeToWait: 5</span><br><span class="line">timeToWait: 5</span><br><span class="line">。。。</span><br></pre></td></tr></table></figure><p>一分钟等得有点长，在启动main时加入VM参数</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">-Darchaius.fixedDelayPollingScheduler.delayMills=2000 -Darchaius.fixedDelayPollingScheduler.initialDelayMills=2000</span><br></pre></td></tr></table></figure><p>只要修改config.properties配置文件，两秒后就能生效。</p><h1 id="api说明"><a href="#api说明" class="headerlink" title="api说明"></a>api说明</h1><h2 id="基本类型动态配置"><a href="#基本类型动态配置" class="headerlink" title="基本类型动态配置"></a>基本类型动态配置</h2><ul><li>DynamicFloatProperty</li><li>DynamicDoubleProperty</li><li>DynamicBooleanProperty</li><li>DynamicStringProperty</li><li>DynamicIntProperty</li><li>DynamicLongProperty</li></ul><p>类图如下：<br><img src="/2018/05/14/netflix-archaius/property.png" alt=""></p><p>基本类型的动态配置继承<code>PropertyWrapper</code>类，实现接口<code>Property</code>，方法说明：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">Property</span><<span class="title">T</span>> </span>{</span><br><span class="line"> <span class="comment">//获取动态配置值</span></span><br><span class="line"> <span class="function">T <span class="title">getValue</span><span class="params">()</span></span>;</span><br><span class="line"> <span class="comment">//获取默认值</span></span><br><span class="line"> <span class="function">T <span class="title">getDefaultValue</span><span class="params">()</span></span>;</span><br><span class="line"> <span class="comment">//获取配置名</span></span><br><span class="line"> <span class="function">String <span class="title">getName</span><span class="params">()</span></span>;</span><br><span class="line"> <span class="comment">//获取修改时间戳</span></span><br><span class="line"> <span class="function"><span class="keyword">long</span> <span class="title">getChangedTimestamp</span><span class="params">()</span></span>;</span><br><span class="line"> <span class="comment">//增加修改回调</span></span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">addCallback</span><span class="params">(Runnable callback)</span></span>;</span><br><span class="line"> <span class="comment">//删除所有回调</span></span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">removeAllCallbacks</span><span class="params">()</span></span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>通过<code>DynamicPropertyFactory</code>的单例获取配置项实例</p><h2 id="扩展类型动态配置"><a href="#扩展类型动态配置" class="headerlink" title="扩展类型动态配置"></a>扩展类型动态配置</h2><ul><li><p>DynamicStringListProperty<br>可以动态配置String list</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//String list</span></span><br><span class="line">DynamicStringListProperty prop = <span class="keyword">new</span> DynamicStringListProperty(<span class="string">"test2"</span>, <span class="string">"0|1"</span>, <span class="string">"\\|"</span>);</span><br><span class="line">List<String> list = prop.get();<span class="comment">//获取包含"0","1"的字符串列表</span></span><br></pre></td></tr></table></figure></li><li><p>DynamicStringMapProperty<br>可以动态配置String Map</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//String map</span></span><br><span class="line">DynamicStringMapProperty prop = <span class="keyword">new</span> DynamicStringMapProperty(<span class="string">"test3"</span>, <span class="string">"key1=1,key2=2,key3=3"</span>);</span><br><span class="line">Map<String, String> map = prop.get();</span><br></pre></td></tr></table></figure></li><li><p>DynamicStringSetProperty<br>可以动态配置String set</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//String set</span></span><br><span class="line">DynamicStringSetProperty prop = <span class="keyword">new</span> DynamicStringSetProperty(<span class="string">"test4"</span>, <span class="string">"a,b,c"</span>);</span><br></pre></td></tr></table></figure></li></ul><p>这几个扩展类型内部有个<code>private DynamicStringProperty delegate;</code>属性，通过解析配置字符串创建需要的类型。</p><h2 id="变更回调"><a href="#变更回调" class="headerlink" title="变更回调"></a>变更回调</h2><p>动态配置项通过<code>addCallback</code>方法增加回调函数：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//设置回调</span></span><br><span class="line">timeToWait.addCallback(() -> {</span><br><span class="line"> System.out.println(<span class="string">"timeToWait callback, new value: "</span> + timeToWait.get());</span><br><span class="line">});</span><br></pre></td></tr></table></figure></p><h1 id="指定配置源"><a href="#指定配置源" class="headerlink" title="指定配置源"></a>指定配置源</h1><h2 id="指定配置文件名称"><a href="#指定配置文件名称" class="headerlink" title="指定配置文件名称"></a>指定配置文件名称</h2><p>archauis默认配置源是classpath下的config.properties，可以增加VM启动参数<br><code>-Darchaius.configurationSource.defaultFileName=test.properties</code>来修改文件名称</p><h2 id="指定配置url"><a href="#指定配置url" class="headerlink" title="指定配置url"></a>指定配置url</h2><p>通过启动参数：<br><code>-Darchaius.configurationSource.additionalUrls=file:///c:/config.properties,https://raw.githubusercontent.com/along101/spring-boot-test/master/actuator-test/src/main/resources/application.properties</code>指定配置源的url，以逗号分隔。<br>配置多个url相同配置项，后面的配置会覆盖前面的，classpath下配置文件优先级最低。</p><h1 id="spring-boot集成"><a href="#spring-boot集成" class="headerlink" title="spring boot集成"></a>spring boot集成</h1><p>spring bean初始化完成，属性值从配置文件注入之后，如果修改配置文件，属性值是不会修改的。如果我们想在运行过程中动态的获取配置项，我们可以将spring的Environment注入到bean中，在代码逻辑中从Environment中获取配置：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Autowired</span></span><br><span class="line"><span class="keyword">private</span> Environment env;</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">someMethod</span><span class="params">()</span></span>{</span><br><span class="line"> ...</span><br><span class="line"> String config = environment.getProperty(<span class="string">"someConfig.name"</span>);</span><br><span class="line"> ...</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>这样的代码显得有些臃肿，并且性能也不高，因为environment是由多个配置源组合起来的。我们使用archaius动态配置就简单很多：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">private</span> DynamicStringProperty someConfig=DynamicPropertyFactory.getInstance().getStringProperty(<span class="string">"someConfig.name"</span>, <span class="string">"default"</span>);</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">someMethod</span><span class="params">()</span></span>{</span><br><span class="line"> ...</span><br><span class="line"> String config = someConfig.get();</span><br><span class="line"> ...</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>如果想参数变更后做些业务操作，archaius非常简单：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//某个bean的内部</span></span><br><span class="line"><span class="keyword">private</span> DynamicStringProperty someConfig=DynamicPropertyFactory.getInstance().getStringProperty(<span class="string">"someConfig.name"</span>, <span class="string">"default"</span>);</span><br><span class="line"></span><br><span class="line"><span class="meta">@PostConstruct</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">someMethod</span><span class="params">()</span></span>{</span><br><span class="line"> someConfig.addCallback(() -> {</span><br><span class="line"> System.out.println(<span class="string">"new value: "</span> + someConfig.get());</span><br><span class="line"> <span class="comment">//业务代码</span></span><br><span class="line"> });</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>spring boot中如何集成archaius呢？ spring-cloud-netflix-core自动配置了archaius，集成spring boot，只要加入如下依赖：<br><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>org.springframework.cloud<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>spring-cloud-netflix-core<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>1.2.7.RELEASE<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependency</span>></span></span><br><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>com.netflix.archaius<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>archaius-core<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>0.7.4<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependency</span>></span></span><br></pre></td></tr></table></figure></p><p>编写测试类TestApplication验证:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@SpringBootApplication</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">TestApplication</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Autowired</span></span><br><span class="line"> Environment env;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Autowired</span></span><br><span class="line"> ArchaiusAutoConfiguration archaiusAutoConfiguration;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> DynamicStringProperty archaiusTest =</span><br><span class="line"> DynamicPropertyFactory.getInstance().getStringProperty(<span class="string">"archaius.test"</span>, <span class="string">"test1"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>{</span><br><span class="line"> SpringApplication.run(TestApplication.class, args);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@PostConstruct</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">init</span><span class="params">()</span> </span>{</span><br><span class="line"> System.out.println(<span class="string">"env config: "</span> + env.getProperty(<span class="string">"archaius.test"</span>));</span><br><span class="line"> System.out.println(<span class="string">"archaius config: "</span> + archaiusTest.get());</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>在spring boot配置文件中加入配置：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">archaius.test=archaius-test</span><br></pre></td></tr></table></figure></p><p>运行测试类TestApplication，会在控制台打印出<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">env config: archaius-test</span><br><span class="line">archaius config: archaius-test</span><br></pre></td></tr></table></figure></p><p>说明archaius从spring 的env中拿到配置了。 </p><p>但是这里有个问题，spring boot本身使用了外部配置，比如集成了apollo，<strong>修改配置，archaius配置项是不生效的</strong>。分析spring-cloud-netflix-core的源代码，里面有个ConfigurableEnvironmentConfiguration继承了apache的AbstractConfiguration，将spring Environment进行了封装，实例化后作为配置源加到archaius的组合配置中，并没有像DynamicURLConfiguration那样进行schedule。 </p><p>我们前面对archaius的源代码进行了详细的分析，可以对此进行改进，让spring更新env时，archaius配置项能感知到。首先增加一个配置源类，实现PolledConfigurationSource接口：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Slf</span>4j</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">SpringEnvConfigurationSource</span> <span class="keyword">implements</span> <span class="title">PolledConfigurationSource</span> </span>{</span><br><span class="line"> <span class="comment">//spring的Environment</span></span><br><span class="line"> <span class="keyword">private</span> ConfigurableEnvironment environment;</span><br><span class="line"> <span class="keyword">private</span> PropertySourcesPropertyResolver resolver;</span><br><span class="line"></span><br><span class="line"> SpringEnvConfigurationSource(ConfigurableEnvironment environment) {</span><br><span class="line"> <span class="keyword">this</span>.environment = environment;</span><br><span class="line"> <span class="keyword">this</span>.resolver = <span class="keyword">new</span> PropertySourcesPropertyResolver(<span class="keyword">this</span>.environment.getPropertySources());</span><br><span class="line"> <span class="keyword">this</span>.resolver.setIgnoreUnresolvableNestedPlaceholders(<span class="keyword">true</span>);</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> PollResult <span class="title">poll</span><span class="params">(<span class="keyword">boolean</span> initial, Object checkPoint)</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> log.debug(<span class="string">"archaius config refresh."</span>);</span><br><span class="line"> <span class="comment">//poll是从spring env中拉取配置</span></span><br><span class="line"> <span class="keyword">return</span> PollResult.createFull(getProperties());</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> Map<String, Object> <span class="title">getProperties</span><span class="params">()</span> </span>{</span><br><span class="line"> Map<String, Object> properties = <span class="keyword">new</span> LinkedHashMap<>();</span><br><span class="line"> <span class="comment">//spring env 里面也是多个source组合的</span></span><br><span class="line"> <span class="keyword">for</span> (Map.Entry<String, PropertySource<?>> entry : getPropertySources().entrySet()) {</span><br><span class="line"> PropertySource<?> source = entry.getValue();</span><br><span class="line"> <span class="keyword">if</span> (source <span class="keyword">instanceof</span> EnumerablePropertySource) {</span><br><span class="line"> EnumerablePropertySource<?> enumerable = (EnumerablePropertySource<?>) source;</span><br><span class="line"> <span class="keyword">for</span> (String name : enumerable.getPropertyNames()) {</span><br><span class="line"> <span class="keyword">if</span> (!properties.containsKey(name)) {</span><br><span class="line"> properties.put(name, resolver.getProperty(name));</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> properties;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">//PropertySource也可能是组合的，通过递归获取</span></span><br><span class="line"> <span class="keyword">private</span> Map<String, PropertySource<?>> getPropertySources() {</span><br><span class="line"> Map<String, PropertySource<?>> map = <span class="keyword">new</span> LinkedHashMap<String, PropertySource<?>>();</span><br><span class="line"> MutablePropertySources sources = <span class="keyword">null</span>;</span><br><span class="line"> <span class="keyword">if</span> (environment != <span class="keyword">null</span>) {</span><br><span class="line"> sources = environment.getPropertySources();</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> sources = <span class="keyword">new</span> StandardEnvironment().getPropertySources();</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">for</span> (PropertySource<?> source : sources) {</span><br><span class="line"> extract(<span class="string">""</span>, map, source);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> map;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title">extract</span><span class="params">(String root, Map<String, PropertySource<?>> map,</span></span></span><br><span class="line"><span class="function"><span class="params"> PropertySource<?> source)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (source <span class="keyword">instanceof</span> CompositePropertySource) {</span><br><span class="line"> <span class="keyword">for</span> (PropertySource<?> nest : ((CompositePropertySource) source)</span><br><span class="line"> .getPropertySources()) {</span><br><span class="line"> extract(source.getName() + <span class="string">":"</span>, map, nest);</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> map.put(root + source.getName(), source);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>这段代码是参考spring-cloud-netflix-core中的ConfigurableEnvironmentConfiguration实现的。<br>然后编写自动配置类代码：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="meta">@ConfigurationProperties</span>(<span class="string">"archaius"</span>)</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ArchaiusConfig</span> <span class="keyword">implements</span> <span class="title">EnvironmentAware</span>, <span class="title">InitializingBean</span> </span>{</span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> String CONFIG_NAME = <span class="string">"springEnv"</span>;</span><br><span class="line"> <span class="meta">@Setter</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">int</span> pollDelayMillis = <span class="number">5000</span>;</span><br><span class="line"> <span class="meta">@Setter</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">int</span> poolInitialDelayMillis = <span class="number">5000</span>;</span><br><span class="line"> <span class="meta">@Setter</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">boolean</span> pollIgnoreDeletesFromSource = <span class="keyword">false</span>;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">private</span> Environment environment;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setEnvironment</span><span class="params">(Environment environment)</span> </span>{</span><br><span class="line"> <span class="keyword">this</span>.environment = environment;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">afterPropertiesSet</span><span class="params">()</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> SpringEnvConfigurationSource springEnvConfigurationSource = <span class="keyword">new</span> SpringEnvConfigurationSource((ConfigurableEnvironment) <span class="keyword">this</span>.environment);</span><br><span class="line"> <span class="comment">//新建一个PollingScheduler</span></span><br><span class="line"> FixedDelayPollingScheduler scheduler = <span class="keyword">new</span> FixedDelayPollingScheduler(poolInitialDelayMillis, pollDelayMillis, pollIgnoreDeletesFromSource);</span><br><span class="line"> ConcurrentMapConfiguration configuration = <span class="keyword">new</span> ConcurrentCompositeConfiguration();</span><br><span class="line"> <span class="comment">//开始轮询，从SpringEnvConfigurationSource中拉取，archaius内部会比较配置的变化</span></span><br><span class="line"> scheduler.startPolling(springEnvConfigurationSource, configuration);</span><br><span class="line"></span><br><span class="line"> <span class="comment">//初始化archaius，这段代码也是参考spring-cloud-netflix-core的</span></span><br><span class="line"> <span class="keyword">if</span> (ConfigurationManager.isConfigurationInstalled()) {</span><br><span class="line"> AbstractConfiguration installedConfiguration = ConfigurationManager.getConfigInstance();</span><br><span class="line"> <span class="keyword">if</span> (installedConfiguration <span class="keyword">instanceof</span> ConcurrentCompositeConfiguration) {</span><br><span class="line"> ConcurrentCompositeConfiguration configInstance = (ConcurrentCompositeConfiguration) installedConfiguration;</span><br><span class="line"> <span class="keyword">if</span> (configInstance.getConfiguration(CONFIG_NAME) == <span class="keyword">null</span>)</span><br><span class="line"> configInstance.addConfigurationAtFront(configuration, CONFIG_NAME);</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> ConcurrentCompositeConfiguration concurrentCompositeConfiguration = <span class="keyword">new</span> ConcurrentCompositeConfiguration();</span><br><span class="line"> concurrentCompositeConfiguration.addConfiguration(configuration, CONFIG_NAME);</span><br><span class="line"> ConfigurationManager.install(concurrentCompositeConfiguration);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>修改启动类进行测试：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@SpringBootApplication</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">TestApplication</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Autowired</span></span><br><span class="line"> ConfigurableEnvironment env;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Autowired</span></span><br><span class="line"> ArchaiusAutoConfiguration archaiusAutoConfiguration;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> DynamicStringProperty archaiusTest =</span><br><span class="line"> DynamicPropertyFactory.getInstance().getStringProperty(<span class="string">"archaius.test"</span>, <span class="string">"test1"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException </span>{</span><br><span class="line"> SpringApplication.run(TestApplication.class, args);</span><br><span class="line"> Thread.sleep(<span class="number">50000</span> * <span class="number">1000</span>);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@PostConstruct</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">init</span><span class="params">()</span> </span>{</span><br><span class="line"> System.out.println(<span class="string">"env config: "</span> + env.getProperty(<span class="string">"archaius.test"</span>));</span><br><span class="line"> System.out.println(<span class="string">"archaius config: "</span> + archaiusTest.get());</span><br><span class="line"> <span class="comment">//给env中增加一个配置源</span></span><br><span class="line"> MutablePropertySources sources = env.getPropertySources();</span><br><span class="line"> Map<String, Object> config = <span class="keyword">new</span> HashMap<>();</span><br><span class="line"> config.put(<span class="string">"archaius.test"</span>, <span class="string">"map change"</span>);</span><br><span class="line"> <span class="comment">//自定义的配置源加到最前面</span></span><br><span class="line"> sources.addFirst(<span class="keyword">new</span> MapPropertySource(<span class="string">"myMap"</span>, config));</span><br><span class="line"> <span class="keyword">new</span> Thread(<span class="keyword">new</span> Runnable() {</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">run</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="keyword">int</span> i = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">while</span> (<span class="keyword">true</span>) {</span><br><span class="line"> Thread.sleep(<span class="number">2</span> * <span class="number">1000</span>);</span><br><span class="line"> <span class="comment">//打印archaius配置项</span></span><br><span class="line"> System.out.println(<span class="string">"archaius config: "</span> + archaiusTest.get());</span><br><span class="line"> i++;</span><br><span class="line"> <span class="comment">//修改配置源</span></span><br><span class="line"> config.put(<span class="string">"archaius.test"</span>, <span class="string">"map change "</span> + i);</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">catch</span> (Exception e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }).start();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>运行结果：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">env config: archaius-test</span><br><span class="line">archaius config: archaius-test</span><br><span class="line">...</span><br><span class="line">archaius config: map change</span><br><span class="line">archaius config: map change</span><br><span class="line">archaius config: map change 2</span><br><span class="line">archaius config: map change 2</span><br><span class="line">archaius config: map change 2</span><br><span class="line">archaius config: map change 5</span><br><span class="line">archaius config: map change 5</span><br><span class="line">archaius config: map change 7</span><br><span class="line">archaius config: map change 7</span><br></pre></td></tr></table></figure></p><p>可以看到不是每次修改都会生效，轮询时间在ArchaiusConfig中进行的配置。代码地址：<a href="https://github.com/along101/spring-boot-test/tree/5ad5158732ea363aa4fb5b9b965c08977699a9c6/archaius-test" target="_blank" rel="noopener">https://github.com/along101/spring-boot-test/tree/5ad5158732ea363aa4fb5b9b965c08977699a9c6/archaius-test</a></p><p>就这么几十行代码就可以将archaius与spring boot结合起来了。</p><h1 id="源码分析"><a href="#源码分析" class="headerlink" title="源码分析"></a>源码分析</h1><p>archaius源码不多，重点在配置的初始化和动态变更这块。</p><h2 id="初始化配置"><a href="#初始化配置" class="headerlink" title="初始化配置"></a>初始化配置</h2><p>初始化入口是<code>DynamicPropertyFactory.getInstance()</code>，来看看该方法源码<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> DynamicPropertyFactory <span class="title">getInstance</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (config == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">synchronized</span> (ConfigurationManager.class) {</span><br><span class="line"> <span class="keyword">if</span> (config == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">//先初始化AbstractConfiguration</span></span><br><span class="line"> AbstractConfiguration configFromManager = ConfigurationManager.getConfigInstance();</span><br><span class="line"> <span class="keyword">if</span> (configFromManager != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">//初始化自己</span></span><br><span class="line"> initWithConfigurationSource(configFromManager);</span><br><span class="line"> initializedWithDefaultConfig = !ConfigurationManager.isConfigurationInstalled();</span><br><span class="line"> logger.info(<span class="string">"DynamicPropertyFactory is initialized with configuration sources: "</span> + configFromManager);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> instance;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p><code>ConfigurationManager</code>的静态代码块中执行</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">static</span>{</span><br><span class="line"> ...省略部分代码</span><br><span class="line"></span><br><span class="line"> <span class="comment">//设置部署上下文，会初始化environment、datacenter、applicationId、serverId、region等等，不配置的话，就为空</span></span><br><span class="line"> setDeploymentContext(<span class="keyword">new</span> ConfigurationBasedDeploymentContext());</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>经过一层层调用，调用到<code>createDefaultConfigInstance</code>来创建<code>AbstractConfiguration</code>：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">private</span> <span class="keyword">static</span> AbstractConfiguration <span class="title">createDefaultConfigInstance</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="comment">//新建一个组合配置，配置列表中自带一个ConcurrentMapConfiguration，这个配置是containerConfiguration，容器自己的配置</span></span><br><span class="line"> ConcurrentCompositeConfiguration config = <span class="keyword">new</span> ConcurrentCompositeConfiguration(); </span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//增加一个DynamicURLConfiguration，获取默认配置文件url和配置系统属性archaius.configurationSource.additionalUrls得到的url</span></span><br><span class="line"> <span class="comment">//构造函数最后，开启线程定时从url里面更新配置</span></span><br><span class="line"> DynamicURLConfiguration defaultURLConfig = <span class="keyword">new</span> DynamicURLConfiguration();</span><br><span class="line"> config.addConfiguration(defaultURLConfig, URL_CONFIG_NAME);</span><br><span class="line"> } <span class="keyword">catch</span> (Throwable e) {</span><br><span class="line"> logger.warn(<span class="string">"Failed to create default dynamic configuration"</span>, e);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (!Boolean.getBoolean(DISABLE_DEFAULT_SYS_CONFIG)) {</span><br><span class="line"> <span class="comment">//增加SystemConfiguration</span></span><br><span class="line"> SystemConfiguration sysConfig = <span class="keyword">new</span> SystemConfiguration();</span><br><span class="line"> config.addConfiguration(sysConfig, SYS_CONFIG_NAME);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (!Boolean.getBoolean(DISABLE_DEFAULT_ENV_CONFIG)) {</span><br><span class="line"> <span class="comment">//增加环境配置</span></span><br><span class="line"> EnvironmentConfiguration envConfig = <span class="keyword">new</span> EnvironmentConfiguration();</span><br><span class="line"> config.addConfiguration(envConfig, ENV_CONFIG_NAME);</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//增加app的组合配置</span></span><br><span class="line"> ConcurrentCompositeConfiguration appOverrideConfig = <span class="keyword">new</span> ConcurrentCompositeConfiguration();</span><br><span class="line"> config.addConfiguration(appOverrideConfig, APPLICATION_PROPERTIES);</span><br><span class="line"> config.setContainerConfigurationIndex(config.getIndexOfConfiguration(appOverrideConfig));</span><br><span class="line"> <span class="keyword">return</span> config;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>初始化完后，得到一个组合配置，包含5个配置，顺序为：</p><ul><li>URL_CONFIG_NAME 通过url拉取的配置</li><li>SYS_CONFIG_NAME 系统属性配置,通过<code>System.getProperties()</code>获取的配置</li><li>ENV_CONFIG_NAME 环境配置,通过<code>System.getenv()</code>获取的配置</li><li>containerConfiguration 容器配置，<code>ConfigurationManager.getConfigInstance().setProperty(key,value)</code>设置的配置</li><li>APPLICATION_PROPERTIES 调用<code>configurationManager.loadAppOverrideProperties</code>设置的配置</li></ul><p><img src="/2018/05/14/netflix-archaius/config.png" alt=""></p><p>这样就生成了<code>AbstractConfiguration</code>，保存在<code>ConfigurationManager.instance</code>静态变量上。 </p><p>回到<code>DynamicPropertyFactory</code>代码里面，生成了<code>AbstractConfiguration configFromManager</code>之后，调用方法<code>initWithConfigurationSource</code>初始化：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> DynamicPropertyFactory <span class="title">initWithConfigurationSource</span><span class="params">(AbstractConfiguration config)</span> </span>{</span><br><span class="line"></span><br><span class="line"> 。。。</span><br><span class="line"> <span class="comment">//包装config为DynamicPropertySupport</span></span><br><span class="line"> <span class="keyword">return</span> initWithConfigurationSource(<span class="keyword">new</span> ConfigurationBackedDynamicPropertySupportImpl(config));</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>后面会设置<code>setDirect</code>，将<code>DynamicPropertySupport</code>注册到<code>DynamicProperty</code>中<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">static</span> <span class="keyword">void</span> <span class="title">setDirect</span><span class="params">(DynamicPropertySupport support)</span> </span>{</span><br><span class="line"> <span class="keyword">synchronized</span> (ConfigurationManager.class) {</span><br><span class="line"> config = support;</span><br><span class="line"> DynamicProperty.registerWithDynamicPropertySupport(support);</span><br><span class="line"> initializedWithDefaultConfig = <span class="keyword">false</span>;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p><code>DynamicProperty</code>注册<code>DynamicPropertySupport</code>的过程是增加一个<code>DynamicPropertyListener</code>，更新所有的属性，也就是更新他的静态变量<code>ALL_PROPS</code>里面的配置项<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">static</span> <span class="keyword">synchronized</span> <span class="keyword">void</span> <span class="title">initialize</span><span class="params">(DynamicPropertySupport config)</span> </span>{</span><br><span class="line"> dynamicPropertySupportImpl = config;</span><br><span class="line"> config.addConfigurationListener(<span class="keyword">new</span> DynamicPropertyListener());</span><br><span class="line"> updateAllProperties();</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>到这里就初始化完了。根据以上源代码的分析，我们画出类图如下：</p><p><img src="/2018/05/14/netflix-archaius/init.png" alt=""></p><p>这里最重要的两个类是</p><ul><li><code>ConfigurationManager</code> 静态变量<code>AbstractConfiguration instance为</code>所有配置项信息</li><li><code>DynamicProperty</code> 静态变量<code>DynamicPropertySupport dynamicPropertySupportImpl</code>用于动态更新，静态变量<code>ConcurrentHashMap<String, DynamicProperty> ALL_PROPS</code>为被使用的动态属性</li></ul><h2 id="获取配置"><a href="#获取配置" class="headerlink" title="获取配置"></a>获取配置</h2><p>通过以下代码获取动态配置：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">DynamicLongProperty timeToWait =</span><br><span class="line"> DynamicPropertyFactory.getInstance().getLongProperty(<span class="string">"lock.waitTime"</span>, <span class="number">1000</span>);</span><br></pre></td></tr></table></figure></p><p>进入<code>getLongProperty</code>方法：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> DynamicLongProperty <span class="title">getLongProperty</span><span class="params">(String propName, <span class="keyword">long</span> defaultValue, <span class="keyword">final</span> Runnable propertyChangeCallback)</span> </span>{</span><br><span class="line"> <span class="comment">//检查初始化</span></span><br><span class="line"> checkAndWarn(propName);</span><br><span class="line"> <span class="comment">//新建一个动态配置</span></span><br><span class="line"> DynamicLongProperty property = <span class="keyword">new</span> DynamicLongProperty(propName, defaultValue);</span><br><span class="line"> <span class="comment">//增加回调</span></span><br><span class="line"> addCallback(propertyChangeCallback, property);</span><br><span class="line"> <span class="keyword">return</span> property;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p><code>DynamicLongProperty</code>继承了<code>PropertyWrapper</code>，含有属性<code>DynamicProperty prop</code>，先初始化该属性：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">this</span>.prop = DynamicProperty.getInstance(propName);</span><br></pre></td></tr></table></figure></p><p>再往下看：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> DynamicProperty <span class="title">getInstance</span><span class="params">(String propName)</span> </span>{</span><br><span class="line"> <span class="comment">//dynamicPropertySupportImpl为空，先初始化DynamicPropertyFactory</span></span><br><span class="line"> <span class="keyword">if</span> (dynamicPropertySupportImpl == <span class="keyword">null</span>) {</span><br><span class="line"> DynamicPropertyFactory.getInstance();</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//从ALL_PROPS中获取prop，没有的话，新建，并放到ALL_PROPS中</span></span><br><span class="line"> <span class="comment">//这里没有加同步设置，但是做了个小动作，没有并发问题</span></span><br><span class="line"> DynamicProperty prop = ALL_PROPS.get(propName);</span><br><span class="line"> <span class="keyword">if</span> (prop == <span class="keyword">null</span>) {</span><br><span class="line"> prop = <span class="keyword">new</span> DynamicProperty(propName);</span><br><span class="line"> <span class="comment">//ALL_PROPS是ConcurrentHashMap，putIfAbsent是线程安全的，存在的话返回老的值</span></span><br><span class="line"> DynamicProperty oldProp = ALL_PROPS.putIfAbsent(propName, prop);</span><br><span class="line"> <span class="comment">//oldProp不为null，返回oldProp，解决了并发的问题，副作用是多建了DynamicProperty对象</span></span><br><span class="line"> <span class="keyword">if</span> (oldProp != <span class="keyword">null</span>) {</span><br><span class="line"> prop = oldProp;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> prop;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>再看<code>new DynamicProperty(propName)</code></p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br></pre></td><td class="code"><pre><span class="line"> <span class="function"><span class="keyword">private</span> <span class="title">DynamicProperty</span><span class="params">(String propName)</span> </span>{</span><br><span class="line"> <span class="comment">//设置属性名称</span></span><br><span class="line"> <span class="keyword">this</span>.propName = propName;</span><br><span class="line"> updateValue();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"><span class="comment">//更新属性值</span></span><br><span class="line"><span class="function"><span class="keyword">private</span> <span class="keyword">boolean</span> <span class="title">updateValue</span><span class="params">()</span> </span>{</span><br><span class="line"> String newValue;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="keyword">if</span> (dynamicPropertySupportImpl != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">//从dynamicPropertySupportImpl中获取配置项，这里是包装AbstractConfiguration的，也就是在ConfigurationManager中的instance</span></span><br><span class="line"> newValue = dynamicPropertySupportImpl.getString(propName);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">false</span>;</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">catch</span> (Exception e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> logger.error(<span class="string">"Unable to update property: "</span> + propName, e);</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">false</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> updateValue(newValue);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">boolean</span> <span class="title">updateValue</span><span class="params">(Object newValue)</span> </span>{</span><br><span class="line"> String nv = (newValue == <span class="keyword">null</span>) ? <span class="keyword">null</span> : newValue.toString();</span><br><span class="line"> <span class="keyword">synchronized</span> (lock) {</span><br><span class="line"> <span class="keyword">if</span> ((nv == <span class="keyword">null</span> && stringValue == <span class="keyword">null</span>)</span><br><span class="line"> || (nv != <span class="keyword">null</span> && nv.equals(stringValue))) {</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">false</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//更新stringValue</span></span><br><span class="line"> stringValue = nv;</span><br><span class="line"> <span class="comment">//刷新缓存</span></span><br><span class="line"> cachedStringValue.flush();</span><br><span class="line"> booleanValue.flush();</span><br><span class="line"> integerValue.flush();</span><br><span class="line"> floatValue.flush();</span><br><span class="line"> classValue.flush();</span><br><span class="line"> doubleValue.flush();</span><br><span class="line"> longValue.flush();</span><br><span class="line"> changedTime = System.currentTimeMillis();</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">true</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure><p>到这里<code>DynamicLongProperty</code>对象就新建了，里面包含一个<code>DynamicProperty</code>，配置值的更新、回调都是由这个<code>DynamicProperty</code>完成的，他的属性有：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//配置名称</span></span><br><span class="line"><span class="keyword">private</span> String propName;</span><br><span class="line"><span class="comment">//配置的值，原始string</span></span><br><span class="line"><span class="keyword">private</span> String stringValue = <span class="keyword">null</span>;</span><br><span class="line"><span class="comment">//更新时间</span></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">long</span> changedTime;</span><br><span class="line"><span class="comment">//回到函数表</span></span><br><span class="line"><span class="keyword">private</span> CopyOnWriteArraySet<Runnable> callbacks = <span class="keyword">new</span> CopyOnWriteArraySet<Runnable>();</span><br><span class="line"></span><br><span class="line"><span class="comment">//缓存的StringValue</span></span><br><span class="line"><span class="keyword">private</span> CachedValue<String> cachedStringValue = <span class="keyword">new</span> CachedValue<String>() {</span><br><span class="line"> <span class="function"><span class="keyword">protected</span> String <span class="title">parse</span><span class="params">(String rep)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> rep;</span><br><span class="line"> }</span><br><span class="line">};</span><br><span class="line"><span class="comment">//缓存的integerValue</span></span><br><span class="line"><span class="keyword">private</span> CachedValue<Integer> integerValue = <span class="keyword">new</span> CachedValue<Integer>() {</span><br><span class="line"> <span class="function"><span class="keyword">protected</span> Integer <span class="title">parse</span><span class="params">(String rep)</span> <span class="keyword">throws</span> NumberFormatException </span>{</span><br><span class="line"> <span class="keyword">return</span> Integer.valueOf(rep);</span><br><span class="line"> }</span><br><span class="line">};</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> CachedValue<Long> longValue = <span class="keyword">new</span> CachedValue<Long>() {</span><br><span class="line"> <span class="function"><span class="keyword">protected</span> Long <span class="title">parse</span><span class="params">(String rep)</span> <span class="keyword">throws</span> NumberFormatException </span>{</span><br><span class="line"> <span class="keyword">return</span> Long.valueOf(rep);</span><br><span class="line"> }</span><br><span class="line">};</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> CachedValue<Float> floatValue = <span class="keyword">new</span> CachedValue<Float>() {</span><br><span class="line"> <span class="function"><span class="keyword">protected</span> Float <span class="title">parse</span><span class="params">(String rep)</span> <span class="keyword">throws</span> NumberFormatException </span>{</span><br><span class="line"> <span class="keyword">return</span> Float.valueOf(rep);</span><br><span class="line"> }</span><br><span class="line">};</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> CachedValue<Double> doubleValue = <span class="keyword">new</span> CachedValue<Double>() {</span><br><span class="line"> <span class="function"><span class="keyword">protected</span> Double <span class="title">parse</span><span class="params">(String rep)</span> <span class="keyword">throws</span> NumberFormatException </span>{</span><br><span class="line"> <span class="keyword">return</span> Double.valueOf(rep);</span><br><span class="line"> }</span><br><span class="line">};</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> CachedValue<Class> classValue = <span class="keyword">new</span> CachedValue<Class>() {</span><br><span class="line"> <span class="function"><span class="keyword">protected</span> Class <span class="title">parse</span><span class="params">(String rep)</span> <span class="keyword">throws</span> ClassNotFoundException </span>{</span><br><span class="line"> <span class="keyword">return</span> Class.forName(rep);</span><br><span class="line"> }</span><br><span class="line">};</span><br></pre></td></tr></table></figure><p>这个<code>CachedValue</code>是<code>DynamicLongProperty</code>的内部类，缓存了配置的实际值，通过解析<code>DynamicLongProperty</code>的stringValue值获取不同类型的配置值。下面我们来分析这一过程。<code>DynamicLongProperty.get()</code>获取动态配置项的值代码如下：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">long</span> <span class="title">get</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> prop.getLong(defaultValue).longValue();</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>通过内置的prop属性即<code>DynamicProperty</code>获取的配置项，prop中通过属性longValue获取配置项<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> Long <span class="title">getLong</span><span class="params">(Long defaultValue)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> longValue.getValue(defaultValue);</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>前面初始化prop时，会初始化属性<code>CachedValue<Long> longValue</code>：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">private</span> CachedValue<Long> longValue = <span class="keyword">new</span> CachedValue<Long>() {</span><br><span class="line"> <span class="function"><span class="keyword">protected</span> Long <span class="title">parse</span><span class="params">(String rep)</span> <span class="keyword">throws</span> NumberFormatException </span>{</span><br><span class="line"> <span class="keyword">return</span> Long.valueOf(rep);</span><br><span class="line"> }</span><br><span class="line">};</span><br></pre></td></tr></table></figure><p>longValue是一个<code>CachedValue</code>类型，getValue方法如下：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> T <span class="title">getValue</span><span class="params">()</span> <span class="keyword">throws</span> IllegalArgumentException </span>{</span><br><span class="line"> <span class="comment">// Not quite double-check locking -- since isCached is marked as volatile</span></span><br><span class="line"> <span class="keyword">if</span> (!isCached) {</span><br><span class="line"> <span class="keyword">synchronized</span> (lock) {</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//如果配置值DynamicProperty.stringValue为null，则没有该配置项，返回null，否则解析stringValue返回</span></span><br><span class="line"> <span class="comment">//这里的parse方法自然是调用longValue的parse方法返回Long值</span></span><br><span class="line"> value = (stringValue == <span class="keyword">null</span>) ? <span class="keyword">null</span> : parse(stringValue);</span><br><span class="line"> exception = <span class="keyword">null</span>;</span><br><span class="line"> } <span class="keyword">catch</span> (Exception e) {</span><br><span class="line"> value = <span class="keyword">null</span>;</span><br><span class="line"> exception = <span class="keyword">new</span> IllegalArgumentException(e);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> isCached = <span class="keyword">true</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (exception != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">throw</span> exception;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">return</span> value;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>到这里，通过<code>DynamicLongProperty.getLongProperty</code>获取的配置值就能拿到了。其他的<code>DynamicIntProperty</code>、<code>DynamicStringProperty</code>等配置项的获取与此相同。</p><h2 id="动态更新"><a href="#动态更新" class="headerlink" title="动态更新"></a>动态更新</h2><p>archaius最有价值的特点是能动态更新配置项，这里动态更新的配置项是指前面我们分析初始化是的<code>DynamicURLConfiguration</code>，我们先看看<code>DynamicURLConfiguration</code>的是如何动态更新的，构造函数：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="title">DynamicURLConfiguration</span><span class="params">()</span> </span>{</span><br><span class="line"> URLConfigurationSource source = <span class="keyword">new</span> URLConfigurationSource();</span><br><span class="line"> <span class="keyword">if</span> (source.getConfigUrls() != <span class="keyword">null</span> && source.getConfigUrls().size() > <span class="number">0</span>) {</span><br><span class="line"> startPolling(source, <span class="keyword">new</span> FixedDelayPollingScheduler());</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>这里的startPolling开始轮询url资源内容，然后更新：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">synchronized</span> <span class="keyword">void</span> <span class="title">startPolling</span><span class="params">(PolledConfigurationSource source, AbstractPollingScheduler scheduler)</span> </span>{</span><br><span class="line"> <span class="keyword">this</span>.scheduler = scheduler;</span><br><span class="line"> <span class="keyword">this</span>.source = source;</span><br><span class="line"> init(source, scheduler);</span><br><span class="line"> <span class="comment">//然后schedule调度轮询</span></span><br><span class="line"> scheduler.startPolling(source, <span class="keyword">this</span>); </span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">startPolling</span><span class="params">(<span class="keyword">final</span> PolledConfigurationSource source, <span class="keyword">final</span> Configuration config)</span> </span>{</span><br><span class="line"> <span class="comment">//先初始化</span></span><br><span class="line"> initialLoad(source, config);</span><br><span class="line"> Runnable r = getPollingRunnable(source, config);</span><br><span class="line"> schedule(r);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">protected</span> <span class="keyword">synchronized</span> <span class="keyword">void</span> <span class="title">schedule</span><span class="params">(Runnable runnable)</span> </span>{</span><br><span class="line"><span class="comment">//线程池调度</span></span><br><span class="line"> executor = Executors.newScheduledThreadPool(<span class="number">1</span>, <span class="keyword">new</span> ThreadFactory() {</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> Thread <span class="title">newThread</span><span class="params">(Runnable r)</span> </span>{</span><br><span class="line"> Thread t = <span class="keyword">new</span> Thread(r, <span class="string">"pollingConfigurationSource"</span>);</span><br><span class="line"> t.setDaemon(<span class="keyword">true</span>);</span><br><span class="line"> <span class="keyword">return</span> t;</span><br><span class="line"> }</span><br><span class="line"> });</span><br><span class="line"> executor.scheduleWithFixedDelay(runnable, initialDelayMillis, delayMillis, TimeUnit.MILLISECONDS);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">protected</span> Runnable <span class="title">getPollingRunnable</span><span class="params">(<span class="keyword">final</span> PolledConfigurationSource source, <span class="keyword">final</span> Configuration config)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> Runnable() {</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">run</span><span class="params">()</span> </span>{</span><br><span class="line"> log.debug(<span class="string">"Polling started"</span>);</span><br><span class="line"> PollResult result = <span class="keyword">null</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//重点是这里，拉取配置结果</span></span><br><span class="line"> result = source.poll(<span class="keyword">false</span>, getNextCheckPoint(checkPoint));</span><br><span class="line"> checkPoint = result.getCheckPoint();</span><br><span class="line"> fireEvent(EventType.POLL_SUCCESS, result, <span class="keyword">null</span>);</span><br><span class="line"> } <span class="keyword">catch</span> (Throwable e) {</span><br><span class="line"> log.error(<span class="string">"Error getting result from polling source"</span>, e);</span><br><span class="line"> fireEvent(EventType.POLL_FAILURE, <span class="keyword">null</span>, e);</span><br><span class="line"> <span class="keyword">return</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//更新配置</span></span><br><span class="line"> populateProperties(result, config);</span><br><span class="line"> } <span class="keyword">catch</span> (Throwable e) {</span><br><span class="line"> log.error(<span class="string">"Error occured applying properties"</span>, e);</span><br><span class="line"> } </span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> }; </span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>以上代码是先初始化，从url中拉取配置，然后开启一个线程，间隔一段时间拉取，然后调用populateProperties方法更新配置。<br>source.poll代码比较简单，获取url资源，得到Properties，转换为map，封装在<code>PollResult</code>中</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> PollResult <span class="title">poll</span><span class="params">(<span class="keyword">boolean</span> initial, Object checkPoint)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> IOException </span>{ </span><br><span class="line"> <span class="keyword">if</span> (configUrls == <span class="keyword">null</span> || configUrls.length == <span class="number">0</span>) {</span><br><span class="line"> <span class="keyword">return</span> PollResult.createFull(<span class="keyword">null</span>);</span><br><span class="line"> }</span><br><span class="line"> Map<String, Object> map = <span class="keyword">new</span> HashMap<String, Object>();</span><br><span class="line"> <span class="keyword">for</span> (URL url: configUrls) {</span><br><span class="line"> InputStream fin = url.openStream();</span><br><span class="line"> Properties props = ConfigurationUtils.loadPropertiesFromInputStream(fin);</span><br><span class="line"> <span class="keyword">for</span> (Entry<Object, Object> entry: props.entrySet()) {</span><br><span class="line"> map.put((String) entry.getKey(), entry.getValue());</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> PollResult.createFull(map);</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>populateProperties更新配置的代码：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title">populateProperties</span><span class="params">(<span class="keyword">final</span> PollResult result, <span class="keyword">final</span> Configuration config)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (result == <span class="keyword">null</span> || !result.hasChanges()) {</span><br><span class="line"> <span class="keyword">return</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (!result.isIncremental()) {</span><br><span class="line"> <span class="comment">//不是增量结果，即全量结果，默认使用的是全量结果</span></span><br><span class="line"> Map<String, Object> props = result.getComplete();</span><br><span class="line"> <span class="keyword">if</span> (props == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">return</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//遍历每个配置项，进行更新</span></span><br><span class="line"> <span class="keyword">for</span> (Entry<String, Object> entry: props.entrySet()) {</span><br><span class="line"> propertyUpdater.addOrChangeProperty(entry.getKey(), entry.getValue(), config);</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//下面这段逻辑是删除配置项</span></span><br><span class="line"> HashSet<String> existingKeys = <span class="keyword">new</span> HashSet<String>();</span><br><span class="line"> <span class="keyword">for</span> (Iterator<String> i = config.getKeys(); i.hasNext();) {</span><br><span class="line"> existingKeys.add(i.next());</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (!ignoreDeletesFromSource) {</span><br><span class="line"> <span class="keyword">for</span> (String key: existingKeys) {</span><br><span class="line"> <span class="keyword">if</span> (!props.containsKey(key)) {</span><br><span class="line"> propertyUpdater.deleteProperty(key, config);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">//增量结果，默认情况下是全量，一般不会走这里</span></span><br><span class="line"> 。。。</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure></p><p>先遍历所有配置项进行更新，然后处理删除配置项。通过propertyUpdater.addOrChangeProperty更新配置型，代码：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">addOrChangeProperty</span><span class="params">(<span class="keyword">final</span> String name, <span class="keyword">final</span> Object newValue, <span class="keyword">final</span> Configuration config)</span> </span>{</span><br><span class="line"> <span class="comment">// We do not want to abort the operation due to failed validation on one property</span></span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//config中不包含配置项就增加</span></span><br><span class="line"> <span class="keyword">if</span> (!config.containsKey(name)) {</span><br><span class="line"> logger.debug(<span class="string">"adding property key [{}], value [{}]"</span>, name, newValue);</span><br><span class="line"></span><br><span class="line"> config.addProperty(name, newValue);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">//包含的话就比较</span></span><br><span class="line"> Object oldValue = config.getProperty(name);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">if</span> (newValue != <span class="keyword">null</span>) {</span><br><span class="line"> Object newValueArray;</span><br><span class="line"> <span class="comment">//数组处理</span></span><br><span class="line"> <span class="keyword">if</span> (oldValue <span class="keyword">instanceof</span> CopyOnWriteArrayList && AbstractConfiguration.getDefaultListDelimiter() != <span class="string">'\0'</span>){</span><br><span class="line"> newValueArray =</span><br><span class="line"> <span class="keyword">new</span> CopyOnWriteArrayList();</span><br><span class="line"></span><br><span class="line"> Iterable<String> stringiterator = Splitter.on(AbstractConfiguration.getDefaultListDelimiter()).omitEmptyStrings().trimResults().split((String)newValue);</span><br><span class="line"> <span class="keyword">for</span>(String s :stringiterator){</span><br><span class="line"> ((CopyOnWriteArrayList) newValueArray).add(s);</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> newValueArray = newValue;</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//不相同修改配置</span></span><br><span class="line"> <span class="keyword">if</span> (!newValueArray.equals(oldValue)) {</span><br><span class="line"> logger.debug(<span class="string">"updating property key [{}], value [{}]"</span>, name, newValue);</span><br><span class="line"></span><br><span class="line"> config.setProperty(name, newValue);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (oldValue != <span class="keyword">null</span>) {</span><br><span class="line"> logger.debug(<span class="string">"nulling out property key [{}]"</span>, name);</span><br><span class="line"></span><br><span class="line"> config.setProperty(name, <span class="keyword">null</span>);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">catch</span> (ValidationException e) {</span><br><span class="line"> logger.warn(<span class="string">"Validation failed for property "</span> + name, e);</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure><p>更新配置项的过程是拿出老的配置值跟新的配置值进行比较，不相同才修改，还处理了下数组配置项。这里的config是<code>DynamicURLConfiguration</code>，setProperty方法中触发事件：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setProperty</span><span class="params">(String key, Object value)</span> <span class="keyword">throws</span> ValidationException</span></span><br><span class="line"><span class="function"></span>{</span><br><span class="line"> <span class="keyword">if</span> (value == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> NullPointerException(<span class="string">"Value for property "</span> + key + <span class="string">" is null"</span>);</span><br><span class="line"> }</span><br><span class="line"> fireEvent(EVENT_SET_PROPERTY, key, value, <span class="keyword">true</span>);</span><br><span class="line"> setPropertyImpl(key, value);</span><br><span class="line"> fireEvent(EVENT_SET_PROPERTY, key, value, <span class="keyword">false</span>);</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>setPropertyImpl方法修改<code>DynamicURLConfiguration</code>内部保存的配置项，这里虽然改了<code>DynamicURLConfiguration</code>配置项值，但是真正用到的地方存在<code>DynamicProperty</code>中，触发fireEvent方法才会去修改<code>DynamicProperty</code>中的值：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title">fireEvent</span><span class="params">(<span class="keyword">int</span> type, String propName, Object propValue, <span class="keyword">boolean</span> beforeUpdate)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (listeners == <span class="keyword">null</span> || listeners.size() == <span class="number">0</span>) {</span><br><span class="line"> <span class="keyword">return</span>;</span><br><span class="line"> }</span><br><span class="line"> ConfigurationEvent event = createEvent(type, propName, propValue, beforeUpdate);</span><br><span class="line"> <span class="comment">//通知每个监听器，这里listeners是一个CopyOnWriteArrayList类型，防止在遍历过程中更新数据产生问题</span></span><br><span class="line"> <span class="keyword">for</span> (ConfigurationListener l: listeners)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> l.configurationChanged(event);</span><br><span class="line"> } <span class="keyword">catch</span> (ValidationException e) {</span><br><span class="line"> <span class="keyword">if</span> (beforeUpdate) {</span><br><span class="line"> <span class="keyword">throw</span> e;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> logger.error(<span class="string">"Unexpected exception"</span>, e); </span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">catch</span> (Throwable e) {</span><br><span class="line"> logger.error(<span class="string">"Error firing configuration event"</span>, e);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p><code>DynamicURLConfiguration</code>添加到<code>ConcurrentCompositeConfiguration</code>中时，<code>ConcurrentCompositeConfiguration</code>会给每个Configuration增加一个<code>ConfigurationListener eventPropagater</code>:<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">addConfigurationAtIndex</span><span class="params">(AbstractConfiguration config, String name, <span class="keyword">int</span> index)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> IndexOutOfBoundsException </span>{</span><br><span class="line"> <span class="keyword">if</span> (!configList.contains(config)) {</span><br><span class="line"> checkIndex(index);</span><br><span class="line"> configList.add(index, config);</span><br><span class="line"> <span class="keyword">if</span> (name != <span class="keyword">null</span>) {</span><br><span class="line"> namedConfigurations.put(name, config);</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//将自己的属性eventPropagater添加到config的监听列表中</span></span><br><span class="line"> config.addConfigurationListener(eventPropagater);</span><br><span class="line"> fireEvent(EVENT_CONFIGURATION_SOURCE_CHANGED, <span class="keyword">null</span>, <span class="keyword">null</span>, <span class="keyword">false</span>);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> logger.warn(config + <span class="string">" is not added as it already exits"</span>);</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure></p><p><code>DynamicURLConfiguration</code>中就有一个<code>ConfigurationListener</code>的监听器：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//ConcurrentCompositeConfiguration监听器属性初始化</span></span><br><span class="line"><span class="keyword">private</span> ConfigurationListener eventPropagater = <span class="keyword">new</span> ConfigurationListener() {</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">configurationChanged</span><span class="params">(ConfigurationEvent event)</span> </span>{</span><br><span class="line"> <span class="keyword">boolean</span> beforeUpdate = event.isBeforeUpdate();</span><br><span class="line"> <span class="keyword">if</span> (propagateEventToParent) {</span><br><span class="line"> <span class="keyword">int</span> type = event.getType();</span><br><span class="line"> String name = event.getPropertyName();</span><br><span class="line"> Object value = event.getPropertyValue();</span><br><span class="line"> Object finalValue;</span><br><span class="line"> <span class="keyword">switch</span>(type) {</span><br><span class="line"> <span class="keyword">case</span> HierarchicalConfiguration.EVENT_ADD_NODES:</span><br><span class="line"> <span class="keyword">case</span> EVENT_CLEAR:</span><br><span class="line"> <span class="keyword">case</span> EVENT_CONFIGURATION_SOURCE_CHANGED:</span><br><span class="line"> fireEvent(type, name, value, beforeUpdate);</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">case</span> EVENT_ADD_PROPERTY:</span><br><span class="line"> <span class="keyword">case</span> EVENT_SET_PROPERTY:</span><br><span class="line"> <span class="comment">//不管是beforeUpdate是true还是false，都会调用自己的fireEvent方法</span></span><br><span class="line"> <span class="keyword">if</span> (beforeUpdate) {</span><br><span class="line"> <span class="comment">// we want the validators to run even if the source is not</span></span><br><span class="line"> <span class="comment">// the winning configuration</span></span><br><span class="line"> fireEvent(type, name, value, beforeUpdate); </span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> AbstractConfiguration sourceConfig = (AbstractConfiguration) event.getSource();</span><br><span class="line"> AbstractConfiguration winningConf = (AbstractConfiguration) getSource(name);</span><br><span class="line"> <span class="keyword">if</span> (winningConf == <span class="keyword">null</span> || getIndexOfConfiguration(sourceConfig) <= getIndexOfConfiguration(winningConf)) {</span><br><span class="line"> fireEvent(type, name, value, beforeUpdate); </span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> <span class="keyword">case</span> EVENT_CLEAR_PROPERTY:</span><br><span class="line"> finalValue = ConcurrentCompositeConfiguration.<span class="keyword">this</span>.getProperty(name);</span><br><span class="line"> <span class="keyword">if</span> (finalValue == <span class="keyword">null</span>) {</span><br><span class="line"> fireEvent(type, name, value, beforeUpdate); </span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> fireEvent(EVENT_SET_PROPERTY, name, finalValue, beforeUpdate);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> <span class="keyword">default</span>:</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"> } </span><br><span class="line"> } </span><br><span class="line">};</span><br></pre></td></tr></table></figure><p>可以看到，最后都调用<code>ConcurrentCompositeConfiguration</code>的fireEvent方法，fireEvent是从父类继承过来的，作用是调用所有监听器，那么<code>ConcurrentCompositeConfiguration</code>的监听器有哪些呢？我们调试过程中发现有两个：</p><ul><li>ExpandedConfigurationListenerAdapter 配置监听适配器</li><li>ConfigurationBasedDeploymentContext.configListener 部署监听器，环境配置发生改变时，修改环境配置项</li></ul><p>重要的是这个<code>ExpandedConfigurationListenerAdapter</code>，作用是将arhaius定义的监听器适配到Apache定义的监听器上，一个典型的适配器模式。<code>ExpandedConfigurationListenerAdapter</code>含有一个<code>PropertyListener expandedListener</code>属性，实现类是<code>DynamicProperty</code>的内部类<code>DynamicPropertyListener</code>。初始化的地方在<code>DynamicPropertyFactory</code>方法setDirect中：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">static</span> <span class="keyword">void</span> <span class="title">setDirect</span><span class="params">(DynamicPropertySupport support)</span> </span>{</span><br><span class="line"> <span class="keyword">synchronized</span> (ConfigurationManager.class) {</span><br><span class="line"> config = support;</span><br><span class="line"> DynamicProperty.registerWithDynamicPropertySupport(support);</span><br><span class="line"> initializedWithDefaultConfig = <span class="keyword">false</span>;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p><code>DynamicProperty.registerWithDynamicPropertySupport</code>方法：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">static</span> <span class="keyword">void</span> <span class="title">registerWithDynamicPropertySupport</span><span class="params">(DynamicPropertySupport config)</span> </span>{</span><br><span class="line"> initialize(config);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">static</span> <span class="keyword">synchronized</span> <span class="keyword">void</span> <span class="title">initialize</span><span class="params">(DynamicPropertySupport config)</span> </span>{</span><br><span class="line"> dynamicPropertySupportImpl = config;</span><br><span class="line"> <span class="comment">//这里新建DynamicPropertyListener增加到config中</span></span><br><span class="line"> config.addConfigurationListener(<span class="keyword">new</span> DynamicPropertyListener());</span><br><span class="line"> updateAllProperties();</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>这里的config实现类是<code>ConfigurationBackedDynamicPropertySupportImpl</code>，同样是一个适配器模式，将apache的<code>DynamicPropertySupport</code>适配为archaius自己的<code>DynamicPropertySupport</code>，在<code>DynamicProperty</code>里面会用到。我们给出类图：</p><p><img src="/2018/05/14/netflix-archaius/listener.png" alt=""></p><p>根据前面的分析，fireEvent触发的事件最终会适配到<code>DynamicPropertyListener</code>的setProperty方法：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//事件触发中调用setProperty</span></span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setProperty</span><span class="params">(Object source, String name, Object value, <span class="keyword">boolean</span> beforeUpdate)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (!beforeUpdate) {</span><br><span class="line"> updateProperty(name, value);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> validate(name, value);</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"><span class="comment">//更新配置</span></span><br><span class="line"><span class="function"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">boolean</span> <span class="title">updateProperty</span><span class="params">(String propName, Object value)</span> </span>{</span><br><span class="line"> <span class="comment">//从ALL_PROPS中找出动态配置，更新value</span></span><br><span class="line"> DynamicProperty prop = ALL_PROPS.get(propName);</span><br><span class="line"> <span class="keyword">if</span> (prop != <span class="keyword">null</span> && prop.updateValue(value)) {</span><br><span class="line"> <span class="comment">//通知回调</span></span><br><span class="line"> prop.notifyCallbacks();</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">true</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">false</span>;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//更新stringValue值，然后刷新缓存</span></span><br><span class="line"><span class="function"><span class="keyword">boolean</span> <span class="title">updateValue</span><span class="params">(Object newValue)</span> </span>{</span><br><span class="line"> String nv = (newValue == <span class="keyword">null</span>) ? <span class="keyword">null</span> : newValue.toString();</span><br><span class="line"> <span class="keyword">synchronized</span> (lock) {</span><br><span class="line"> <span class="keyword">if</span> ((nv == <span class="keyword">null</span> && stringValue == <span class="keyword">null</span>)</span><br><span class="line"> || (nv != <span class="keyword">null</span> && nv.equals(stringValue))) {</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">false</span>;</span><br><span class="line"> }</span><br><span class="line"> stringValue = nv;</span><br><span class="line"> cachedStringValue.flush();</span><br><span class="line"> booleanValue.flush();</span><br><span class="line"> integerValue.flush();</span><br><span class="line"> floatValue.flush();</span><br><span class="line"> classValue.flush();</span><br><span class="line"> doubleValue.flush();</span><br><span class="line"> longValue.flush();</span><br><span class="line"> changedTime = System.currentTimeMillis();</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">true</span>;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>看到这里，才是真正的将<code>DynamicProperty</code>值更新了，<code>DynamicLongProperty</code>在更新之后获取数据时，会使用新值。 </p><p>接下来我们来看回调，<code>DynamicProperty</code>的notifyCallbacks方法：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">private void notifyCallbacks() {</span><br><span class="line"> //遍历所有的callbacks，执行run</span><br><span class="line"> for (Runnable r : callbacks) {</span><br><span class="line"> try {</span><br><span class="line"> r.run();</span><br><span class="line"> } catch (Exception e) {</span><br><span class="line"> logger.error("Error in DynamicProperty callback", e);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>这里callbacks是<code>DynamicProperty</code>的属性，在给动态配置添加回调函数时，直接添加到<code>DynamicProperty.callbacks</code>属性中，来看<code>PropertyWrapper</code>类的addCallback犯法：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">addCallback</span><span class="params">(Runnable callback)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (callback != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">//这里的prop就是DynamicProperty</span></span><br><span class="line"> prop.addCallback(callback);</span><br><span class="line"> callbackList.add(callback);</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure><p>到这里，动态更新和回调就分析完了。 </p><p>有点复杂，我们再捋一遍：</p><ol><li><code>DynamicURLConfiguration</code>中的线程间隔一段时间从url中拉取配置</li><li>拉取配置后调用<code>AbstractPollingScheduler</code>类的populateProperties方法更新配置</li><li>populateProperties方法中调用属性<code>DynamicPropertyUpdater propertyUpdater</code>的addOrChangeProperty方法</li><li><code>DynamicPropertyUpdater</code>的方法addOrChangeProperty会进行新老配置型对比，调用<code>DynamicURLConfiguration</code>的setProperty方法修改变更项</li><li><code>DynamicURLConfiguration</code>的setProperty方法先修改本身存放的配置项，然后触发事件<code>fireEvent</code></li><li><code>DynamicURLConfiguration</code>中的监听器是<code>ConcurrentCompositeConfiguration</code>的属性<code>ConfigurationListener eventPropagater</code>,<code>ConcurrentCompositeConfiguration</code>每次增加配置源是会给每个源添加eventPropagater监听器</li><li><code>DynamicURLConfiguration</code>的fireEvent会通过eventPropagater触发<code>ConcurrentCompositeConfiguration</code>的fireEvent</li><li><code>ConcurrentCompositeConfiguration</code>的监听器包含一个<code>ExpandedConfigurationListenerAdapter</code>的适配器，包含一个<code>PropertyListener</code>的属性，将事件转到<code>PropertyListener</code>中</li><li><code>PropertyListener</code>的实现类是<code>DynamicProperty</code>的内部类<code>DynamicPropertyListener</code>，里面会调用<code>DynamicProperty</code>的静态方法<code>updateProperty</code></li><li><code>DynamicProperty</code>的<code>updateProperty</code>方法先从<code>ALL_PROPS</code>中获取配置<code>DynamicProperty</code>，更新配置项，然后通知所有的回调。</li></ol>]]></content>
<summary type="html">
<h1 id="archaius介绍"><a href="#archaius介绍" class="headerlink" title="archaius介绍"></a>archaius介绍</h1><p>archaius是Netflix公司开源项目之一，基于java的配置管理类库，主要用于多配置存储的动态获取。主要功能是对apache common configuration类库的扩展。在云平台开发中可以将其用作分布式配置管理依赖构件。同时，它有如下一些特性：</p>
<ul>
<li>动态获取属性</li>
<li>高效和线程安全的配置操作</li>
<li>配置改变时提供回调机制</li>
<li>可以通过jmx操作配置</li>
<li>复合配置</li>
</ul>
</summary>
<category term="spring" scheme="http://along101.site/categories/spring/"/>
<category term="netflix" scheme="http://along101.site/tags/netflix/"/>
<category term="archaius" scheme="http://along101.site/tags/archaius/"/>
<category term="config" scheme="http://along101.site/tags/config/"/>
</entry>
<entry>
<title>java aio socket 原理分析</title>
<link href="http://along101.site/2018/01/29/java-aio-socket/"/>
<id>http://along101.site/2018/01/29/java-aio-socket/</id>
<published>2018-01-29T17:05:57.000Z</published>
<updated>2018-07-20T03:10:04.405Z</updated>
<content type="html"><![CDATA[<h1 id="说明"><a href="#说明" class="headerlink" title="说明"></a>说明</h1><p>Java AIO就是Java作为对异步IO提供支持的NIO.2 ，Java NIO2 (JSR 203)定义了更多的 New I/O APIs， 提案2003提出，直到2011年才发布， 最终在JDK 7中才实现。</p><p>从编程模式上来看AIO相对于NIO的区别在于，NIO需要使用者线程不停的轮询IO对象，来确定是否有数据准备好可以读了，而AIO则是在数据准备好之后，才会通知数据使用者，这样使用者就不需要不停地轮询了。</p><p>当然AIO的异步特性并不是Java实现的伪异步，而是使用了系统底层API的支持，在Unix系统下，采用了epoll IO模型，而windows便是使用了IOCP模型。</p><a id="more"></a><h1 id="java-aio-socket-源代码解析"><a href="#java-aio-socket-源代码解析" class="headerlink" title="java aio socket 源代码解析"></a>java aio socket 源代码解析</h1><p>先上demo，sever端代码如下<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 接收客户端发送数据，返回</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">AIOEchoServer</span> </span>{</span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">final</span> <span class="keyword">int</span> port;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">private</span> AsynchronousServerSocketChannel server = <span class="keyword">null</span>;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="title">AIOEchoServer</span><span class="params">(<span class="keyword">int</span> port)</span> </span>{</span><br><span class="line"> <span class="keyword">this</span>.port = port;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">listen</span><span class="params">()</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> server = AsynchronousServerSocketChannel.open().bind(<span class="keyword">new</span> InetSocketAddress(port));</span><br><span class="line"> <span class="comment">//accept客户端来的连接，生成一个channel，异步回调CompletionHandler</span></span><br><span class="line"> server.accept(<span class="keyword">null</span>, <span class="keyword">new</span> CompletionHandler<AsynchronousSocketChannel, Object>() {</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">completed</span><span class="params">(AsynchronousSocketChannel channel, Object attachment)</span> </span>{</span><br><span class="line"> <span class="comment">//这里得到一个channel，在这个channel上读取数据</span></span><br><span class="line"> ByteBuffer readBuff = ByteBuffer.allocate(<span class="number">1024</span>);</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//如果没有数据可以读取，这个方法会阻塞</span></span><br><span class="line"> channel.read(readBuff, readBuff, <span class="keyword">new</span> CompletionHandler<Integer, ByteBuffer>() {</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">completed</span><span class="params">(Integer result, ByteBuffer readBuff)</span> </span>{</span><br><span class="line"> readBuff.flip();</span><br><span class="line"> <span class="keyword">if</span> (readBuff.remaining() > <span class="number">0</span>) {</span><br><span class="line"> String value = <span class="keyword">new</span> String(readBuff.array(), <span class="number">0</span>, readBuff.limit());</span><br><span class="line"> System.out.println(<span class="string">"receive from client: "</span> + value);</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> value = value + <span class="string">" from server."</span>;</span><br><span class="line"> System.out.println(<span class="string">"write to client: "</span> + value);</span><br><span class="line"> <span class="comment">//写回客户端，用同步的方式，也可以用异步方式。如果客户端数据一次没有读取完，往channel里面写会抛异常，需要粘包</span></span><br><span class="line"> channel.write(ByteBuffer.wrap((value).getBytes())).get();</span><br><span class="line"> } <span class="keyword">catch</span> (Exception e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"> readBuff.clear();</span><br><span class="line"> channel.read(readBuff, readBuff, <span class="keyword">this</span>);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">failed</span><span class="params">(Throwable exc, ByteBuffer attachment)</span> </span>{</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"> });</span><br><span class="line"> } <span class="keyword">catch</span> (Exception e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> <span class="comment">//继续接收其他的客户端连接，如果不加这一行，只能连接一个客户端</span></span><br><span class="line"> server.accept(<span class="keyword">null</span>, <span class="keyword">this</span>);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">failed</span><span class="params">(Throwable exc, Object attachment)</span> </span>{</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"> });</span><br><span class="line"> System.out.println(<span class="string">"Server listen on "</span> + port);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> <span class="keyword">new</span> AIOEchoServer(<span class="number">8001</span>).listen();</span><br><span class="line"> <span class="keyword">while</span> (<span class="keyword">true</span>) {</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> Thread.sleep(<span class="number">100000</span>);</span><br><span class="line"> } <span class="keyword">catch</span> (InterruptedException e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>再看client端：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 向服务端发送一条消息，从服务端读取回执</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">AIOClient</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> <span class="keyword">final</span> AsynchronousSocketChannel clientChannel = AsynchronousSocketChannel.open();</span><br><span class="line"> InetSocketAddress serverAddress = <span class="keyword">new</span> InetSocketAddress(<span class="string">"127.0.0.1"</span>, <span class="number">8001</span>);</span><br><span class="line"> clientChannel.connect(serverAddress).get(<span class="number">1</span>, TimeUnit.SECONDS);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < <span class="number">10</span>; i++) {</span><br><span class="line"> ByteBuffer writeBuffer = ByteBuffer.wrap((<span class="string">"Hello "</span> + i).getBytes());</span><br><span class="line"> <span class="comment">//这里使用一个CountDownLatch，保证从服务端读取回执后再发送下一条，同时使用一个通道发送，会抛异常</span></span><br><span class="line"> CountDownLatch countDownLatch = <span class="keyword">new</span> CountDownLatch(<span class="number">1</span>);</span><br><span class="line"> clientChannel.write(writeBuffer, writeBuffer, <span class="keyword">new</span> CompletionHandler<Integer, ByteBuffer>() {</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">completed</span><span class="params">(Integer result, ByteBuffer writeBuffer)</span> </span>{</span><br><span class="line"> writeBuffer.flip();</span><br><span class="line"> System.out.println(<span class="string">"write success "</span> + <span class="keyword">new</span> String(writeBuffer.array(), <span class="number">0</span>, writeBuffer.limit()));</span><br><span class="line"> ByteBuffer readBuffer = ByteBuffer.allocate(<span class="number">1024</span>);</span><br><span class="line"> <span class="comment">//从服务端读取返回，最多等10秒</span></span><br><span class="line"> clientChannel.read(readBuffer, <span class="number">2</span>, TimeUnit.SECONDS, readBuffer, <span class="keyword">new</span> CompletionHandler<Integer, ByteBuffer>() {</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">completed</span><span class="params">(Integer result, ByteBuffer readBuffer)</span> </span>{</span><br><span class="line"> readBuffer.flip();</span><br><span class="line"> System.out.println(<span class="string">"receive: "</span> + <span class="keyword">new</span> String(readBuffer.array(), <span class="number">0</span>, readBuffer.limit()));</span><br><span class="line"> readBuffer.clear();</span><br><span class="line"> <span class="comment">//读完了才countDown，如果服务端发送数据大于缓冲区大小，这里是处理不了的，还需要进行包的拆分和粘连</span></span><br><span class="line"> countDownLatch.countDown();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">failed</span><span class="params">(Throwable exc, ByteBuffer readBuffer)</span> </span>{</span><br><span class="line"> <span class="comment">//失败了要countDown</span></span><br><span class="line"> countDownLatch.countDown();</span><br><span class="line"> }</span><br><span class="line"> });</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">failed</span><span class="params">(Throwable exc, ByteBuffer attachment)</span> </span>{</span><br><span class="line"> <span class="comment">//失败了要countDown</span></span><br><span class="line"> countDownLatch.countDown();</span><br><span class="line"> }</span><br><span class="line"> });</span><br><span class="line"> countDownLatch.await();</span><br><span class="line"> }</span><br><span class="line"> clientChannel.close();</span><br><span class="line"> System.out.println(<span class="string">"channel close success!"</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>相对于NIO，服务端代码没有Selector，SelectionKey，不需要自己去循环，但是异步方式有些地方比较难以理解。客户端代码像javascript的ajax调用。</p><h1 id="windows上实现"><a href="#windows上实现" class="headerlink" title="windows上实现"></a>windows上实现</h1><h2 id="连接建立"><a href="#连接建立" class="headerlink" title="连接建立"></a>连接建立</h2><h3 id="先看channel的创建"><a href="#先看channel的创建" class="headerlink" title="先看channel的创建"></a>先看channel的创建</h3><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">AsynchronousServerSocketChannel.open()</span><br><span class="line">//往下跟</span><br><span class="line">provider.openAsynchronousServerSocketChannel(group);</span><br><span class="line"></span><br><span class="line"> //windows上，创建一个WindowsAsynchronousServerSocketChannelImpl</span><br><span class="line"> @Override</span><br><span class="line"> public AsynchronousServerSocketChannel openAsynchronousServerSocketChannel(AsynchronousChannelGroup group)</span><br><span class="line"> throws IOException</span><br><span class="line"> {</span><br><span class="line"> return new WindowsAsynchronousServerSocketChannelImpl(toIocp(group));</span><br><span class="line"> }</span><br></pre></td></tr></table></figure><p>我们来看看WindowsAsynchronousServerSocketChannelImpl，是一个异步ServerSockethannelde的实现，包含几个重要属性</p><ul><li>FileDescriptor fd 文件描述符</li><li>InetSocketAddress localAddress 本地地址</li><li>long handle</li><li>int completionKey</li><li>Iocp iocp 一个具体的异步通道组实现</li><li>PendingIoCache ioCache</li><li>long dataBuffer</li><li>AtomicBoolean accepting</li></ul><p>异步通道组的作用是为一组通道提供资源共享，比如异步运行时共享线程池。</p><h3 id="然后是bind本地地址"><a href="#然后是bind本地地址" class="headerlink" title="然后是bind本地地址"></a>然后是bind本地地址</h3><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">try {</span><br><span class="line"> begin();</span><br><span class="line"> synchronized (stateLock) {</span><br><span class="line"> if (localAddress != null)</span><br><span class="line"> throw new AlreadyBoundException();</span><br><span class="line"> NetHooks.beforeTcpBind(fd, isa.getAddress(), isa.getPort());</span><br><span class="line"> Net.bind(fd, isa.getAddress(), isa.getPort());</span><br><span class="line"> Net.listen(fd, backlog < 1 ? 50 : backlog);</span><br><span class="line"> localAddress = Net.localAddress(fd);</span><br><span class="line"> }</span><br><span class="line">} finally {</span><br><span class="line"> end();</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>最后调用的是本地方法，将fd绑定到端口上<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">public static void bind(FileDescriptor fd, InetAddress addr, int port)</span><br><span class="line"> throws IOException</span><br><span class="line">{</span><br><span class="line"> bind(UNSPEC, fd, addr, port);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">static void bind(ProtocolFamily family, FileDescriptor fd,</span><br><span class="line"> InetAddress addr, int port) throws IOException</span><br><span class="line">{</span><br><span class="line"> boolean preferIPv6 = isIPv6Available() &&</span><br><span class="line"> (family != StandardProtocolFamily.INET);</span><br><span class="line"> bind0(fd, preferIPv6, exclusiveBind, addr, port);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">private static native void bind0(FileDescriptor fd, boolean preferIPv6,</span><br><span class="line"> boolean useExclBind, InetAddress addr,</span><br><span class="line"> int port)</span><br><span class="line"> throws IOException;</span><br></pre></td></tr></table></figure></p><h3 id="接下来是AsynchronousServerSocketChannel-accept"><a href="#接下来是AsynchronousServerSocketChannel-accept" class="headerlink" title="接下来是AsynchronousServerSocketChannel.accept"></a>接下来是AsynchronousServerSocketChannel.accept</h3><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">public abstract <A> void accept(A attachment,CompletionHandler<AsynchronousSocketChannel,? super A> handler);</span><br></pre></td></tr></table></figure><p>accept是一个抽象方法，包含两个参数：</p><ul><li>attachment 附加对象，跟nio中注册到Selector上的附加对象一样</li><li>handler accept成功后回调处理逻辑</li></ul><p>accept实现方法：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br></pre></td><td class="code"><pre><span class="line"> //AsynchronousServerSocketChannelImpl类</span><br><span class="line"> public final <A> void accept(A attachment, CompletionHandler<AsynchronousSocketChannel,? super A> handler) {</span><br><span class="line"> if (handler == null)</span><br><span class="line"> throw new NullPointerException("'handler' is null");</span><br><span class="line"> implAccept(attachment, (CompletionHandler<AsynchronousSocketChannel,Object>)handler);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> //WindowsAsynchronousServerSocketChannelImpl类</span><br><span class="line"> @Override</span><br><span class="line"> Future<AsynchronousSocketChannel> implAccept(Object attachment, final CompletionHandler<AsynchronousSocketChannel,Object> handler) {</span><br><span class="line">。。。</span><br><span class="line"> //创建一个被accecped的socket</span><br><span class="line"> WindowsAsynchronousSocketChannelImpl ch = null;</span><br><span class="line"> IOException ioe = null;</span><br><span class="line"> try {</span><br><span class="line"> begin();</span><br><span class="line"> ch = new WindowsAsynchronousSocketChannelImpl(iocp, false);</span><br><span class="line"> } catch (IOException x) {</span><br><span class="line"> ioe = x;</span><br><span class="line"> } finally {</span><br><span class="line"> end();</span><br><span class="line"> }</span><br><span class="line"> //出现异常，直接调用handle</span><br><span class="line"> if (ioe != null) {</span><br><span class="line"> if (handler == null)</span><br><span class="line"> return CompletedFuture.withFailure(ioe);</span><br><span class="line"> Invoker.invokeIndirectly(this, handler, attachment, null, ioe);</span><br><span class="line"> return null;</span><br><span class="line"> }</span><br><span class="line"> //通过getSecurityManager检查</span><br><span class="line"> AccessControlContext acc = (System.getSecurityManager() == null) ? null : AccessController.getContext();</span><br><span class="line"> //PendingFuture实现Future接口，存放this，handler和attachment</span><br><span class="line"> PendingFuture<AsynchronousSocketChannel,Object> result = new PendingFuture<AsynchronousSocketChannel,Object>(this, handler, attachment);</span><br><span class="line"> //AcceptTask实现Runnable接口，</span><br><span class="line"> AcceptTask task = new AcceptTask(ch, acc, result);</span><br><span class="line"> result.setContext(task);</span><br><span class="line"> //并发控制</span><br><span class="line"> if (!accepting.compareAndSet(false, true))</span><br><span class="line"> throw new AcceptPendingException();</span><br><span class="line"></span><br><span class="line"> // 检查操作系统是否支持线程无关的I/O，什么意思？</span><br><span class="line"> if (Iocp.supportsThreadAgnosticIo()) {</span><br><span class="line"> //我的windows上跑这里</span><br><span class="line"> task.run();</span><br><span class="line"> } else {</span><br><span class="line"> Invoker.invokeOnThreadInThreadPool(this, task);</span><br><span class="line"> }</span><br><span class="line"> return result;</span><br><span class="line"> }</span><br></pre></td></tr></table></figure><p>AcceptTask的run方法如下<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"> @Override</span><br><span class="line"> public void run() {</span><br><span class="line"> long overlapped = 0L;</span><br><span class="line">。。。</span><br><span class="line"> synchronized (result) {</span><br><span class="line"> overlapped = ioCache.add(result);</span><br><span class="line"> //重点是这行，调用native方法，windows上直接返回</span><br><span class="line"> int n = accept0(handle, channel.handle(), overlapped, dataBuffer);</span><br><span class="line"> if (n == IOStatus.UNAVAILABLE) {</span><br><span class="line"> return;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> finishAccept();</span><br><span class="line"></span><br><span class="line"> enableAccept();</span><br><span class="line"> //将接收到的channel设置到result中，Future的get方法阻塞就会唤醒</span><br><span class="line"> result.setResult(channel);</span><br><span class="line"> }</span><br><span class="line">。。。</span><br><span class="line"> if (result.isCancelled()) {</span><br><span class="line"> closeChildChannel();</span><br><span class="line"> }</span><br><span class="line"> //最后调用handler，这里Invoker是一个帮助类，实际上是根据是否有异常调用CompletionHandler的completed/failed方法</span><br><span class="line"> Invoker.invokeIndirectly(result);</span><br><span class="line"> }</span><br></pre></td></tr></table></figure></p><p>调试到这里，accept方法实际上已经返回了，那么，当客户端有连接过来的时候，是如何调用回调函数的呢？我们来看看accept0的native方法，打开WindowsAsynchronousServerSocketChannelImpl.c<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br></pre></td><td class="code"><pre><span class="line">JNIEXPORT jint JNICALL</span><br><span class="line">Java_sun_nio_ch_WindowsAsynchronousServerSocketChannelImpl_accept0(JNIEnv* env, jclass this,</span><br><span class="line"> jlong listenSocket, jlong acceptSocket, jlong ov, jlong buf)</span><br><span class="line">{</span><br><span class="line"> BOOL res;</span><br><span class="line"> SOCKET s1 = (SOCKET)jlong_to_ptr(listenSocket);</span><br><span class="line"> SOCKET s2 = (SOCKET)jlong_to_ptr(acceptSocket);</span><br><span class="line"> PVOID outputBuffer = (PVOID)jlong_to_ptr(buf);</span><br><span class="line"></span><br><span class="line"> DWORD nread = 0;</span><br><span class="line"> OVERLAPPED* lpOverlapped = (OVERLAPPED*)jlong_to_ptr(ov);</span><br><span class="line"> ZeroMemory((PVOID)lpOverlapped, sizeof(OVERLAPPED));</span><br><span class="line"> </span><br><span class="line"> res = (*AcceptEx_func)(s1, //一参本地监听Socket </span><br><span class="line"> s2, //二参为即将到来的客人准备好的Socket </span><br><span class="line"> outputBuffer,//三参接收缓冲区： 一存客人发来的第一份数据、二存Server本地地址、三存Client远端地址 地址包括IP和端口， </span><br><span class="line"> 0, //四参定三参数据区长度，0表只连不接收、连接到来->请求完成，否则连接到来+任意长数据到来->请求完成 </span><br><span class="line"> sizeof(SOCKETADDRESS)+16,//五参定三参本地地址区长度，至少sizeof(sockaddr_in) + 16 </span><br><span class="line"> sizeof(SOCKETADDRESS)+16, //六参定三参远端地址区长度，至少sizeof(sockaddr_in) + 16 </span><br><span class="line"> &nread,//标识接收到的字节数</span><br><span class="line"> lpOverlapped);//一个OVERLAPPED结构，传递数据。</span><br><span class="line"> if (res == 0) {</span><br><span class="line"> int error = WSAGetLastError();</span><br><span class="line"> if (error == ERROR_IO_PENDING) {</span><br><span class="line"> return IOS_UNAVAILABLE;</span><br><span class="line"> }</span><br><span class="line"> JNU_ThrowIOExceptionWithLastError(env, "AcceptEx failed");</span><br><span class="line"> return IOS_THROWN;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> return 0;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>看不太明白。。。在看看前面的代码，C语言很多都不记得了，复习了下，搞了个大概<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br></pre></td><td class="code"><pre><span class="line">//定义一个函数指针，后面会指向windows上的函数AcceptEx</span><br><span class="line">typedef BOOL (*AcceptEx_t)</span><br><span class="line">(</span><br><span class="line"> SOCKET sListenSocket,</span><br><span class="line"> SOCKET sAcceptSocket,</span><br><span class="line"> PVOID lpOutputBuffer,</span><br><span class="line"> DWORD dwReceiveDataLength,</span><br><span class="line"> DWORD dwLocalAddressLength,</span><br><span class="line"> DWORD dwRemoteAddressLength,</span><br><span class="line"> LPDWORD lpdwBytesReceived,</span><br><span class="line"> LPOVERLAPPED lpOverlapped</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">//换个名字</span><br><span class="line">static AcceptEx_t AcceptEx_func;</span><br><span class="line"></span><br><span class="line">//native的initIDs方法</span><br><span class="line">JNIEXPORT void JNICALL</span><br><span class="line">Java_sun_nio_ch_WindowsAsynchronousServerSocketChannelImpl_initIDs(JNIEnv* env, jclass this) {</span><br><span class="line"> GUID GuidAcceptEx = WSAID_ACCEPTEX;</span><br><span class="line"> SOCKET s;</span><br><span class="line"> int rv;</span><br><span class="line"> DWORD dwBytes;</span><br><span class="line"></span><br><span class="line"> s = socket(AF_INET, SOCK_STREAM, 0);</span><br><span class="line"> if (s == INVALID_SOCKET) {</span><br><span class="line"> JNU_ThrowIOExceptionWithLastError(env, "socket failed");</span><br><span class="line"> return;</span><br><span class="line"> }</span><br><span class="line"> //windows的WSAIoctl函数</span><br><span class="line"> rv = WSAIoctl(s,</span><br><span class="line"> SIO_GET_EXTENSION_FUNCTION_POINTER,</span><br><span class="line"> (LPVOID)&GuidAcceptEx,</span><br><span class="line"> sizeof(GuidAcceptEx),</span><br><span class="line"> &AcceptEx_func,//给函数指针赋值</span><br><span class="line"> sizeof(AcceptEx_func),</span><br><span class="line"> &dwBytes,</span><br><span class="line"> NULL,</span><br><span class="line"> NULL);</span><br><span class="line"> if (rv != 0)</span><br><span class="line"> JNU_ThrowIOExceptionWithLastError(env, "WSAIoctl failed");</span><br><span class="line"> closesocket(s);</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>这里通过WSAIoctl获取AcceptEx函数指针，供其他地方调用。 </p><p>AcceptEx函数的解释：Windows套接字AcceptEx函数接受一个新的连接，返回本地和远程地址，并接收由客户端应用程序发送的第一块数据。关键点就在这个AcceptEx函数，调用这个函数，立即返回了，实际上没有创建连接，创建一个等待连接的数据结构体放在port指定的队列中，如果来了新的连接（客户端连接，触发事件），会将连接信息填写到结构体中，修改状态。这个连接准备好了，肯定有地方去消费这个连接，在哪里呢？ </p><p>我们回到AsynchronousServerSocketChannel.open()这个位置，这里打开了一个ServerSocket，内部使用了一个Iocp，前面我们没有解释这个Iocp是什么意思，查阅资料发现，这是windows网路编程提出的一个模型，（I/O Completion Port）,常称I/O完成端口。要深入这个模型，又会比较复杂，我们这里先简单的理解下，AcceptEx被调用时，会在serverSocket上注册一个回调，如果有客户端连上来了，操作系统会来处理。如何处理的呢？ AsynchronousServerSocketChannel.open()的时候，会创建一个iocp java对象，内部调用native方法createIoCompletionPort创建windos的 iocp，然后将与serverSocketChannel关联。</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br></pre></td><td class="code"><pre><span class="line">Iocp(AsynchronousChannelProvider provider, ThreadPool pool)</span><br><span class="line"> throws IOException</span><br><span class="line">{</span><br><span class="line"> super(provider, pool);</span><br><span class="line"> //创建Iocp</span><br><span class="line"> this.port =</span><br><span class="line"> createIoCompletionPort(INVALID_HANDLE_VALUE, 0, 0, fixedThreadCount());</span><br><span class="line"> this.nextCompletionKey = 1;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">/**</span><br><span class="line"> * 与serverSocketChannel关联</span><br><span class="line"> */</span><br><span class="line">int associate(OverlappedChannel ch, long handle) throws IOException {</span><br><span class="line"> keyToChannelLock.writeLock().lock();</span><br><span class="line"></span><br><span class="line"> // generate a completion key (if not shutdown)</span><br><span class="line"> int key;</span><br><span class="line"> try {</span><br><span class="line"> if (isShutdown())</span><br><span class="line"> throw new ShutdownChannelGroupException();</span><br><span class="line"></span><br><span class="line"> // generate unique key</span><br><span class="line"> do {</span><br><span class="line"> key = nextCompletionKey++;</span><br><span class="line"> } while ((key == 0) || keyToChannel.containsKey(key));</span><br><span class="line"></span><br><span class="line"> // associate with I/O completion port</span><br><span class="line"> if (handle != 0L) {</span><br><span class="line"> //这里是关联，这里有个key，后面通知的时候，会用到这个key</span><br><span class="line"> createIoCompletionPort(handle, port, key, 0);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // 将key与ch放在hashmao缓存，后面的事件来了，会返回这个key，通过这个key找到channel</span><br><span class="line"> keyToChannel.put(key, ch);</span><br><span class="line"> } finally {</span><br><span class="line"> keyToChannelLock.writeLock().unlock();</span><br><span class="line"> }</span><br><span class="line"> return key;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">//Iocp.java native方法</span><br><span class="line">private static native void initIDs();</span><br><span class="line"></span><br><span class="line">private static native long createIoCompletionPort(long handle,</span><br><span class="line"> long existingPort, int completionKey, int concurrency) throws IOException;</span><br><span class="line"></span><br><span class="line">private static native void close0(long handle);</span><br><span class="line"></span><br><span class="line">private static native void getQueuedCompletionStatus(long completionPort,</span><br><span class="line"> CompletionStatus status) throws IOException;</span><br><span class="line"></span><br><span class="line">private static native void postQueuedCompletionStatus(long completionPort,</span><br><span class="line"> int completionKey) throws IOException;</span><br><span class="line"></span><br><span class="line">private static native String getErrorMessage(int error);</span><br></pre></td></tr></table></figure><p>然后启动一个线程，阻塞在getQueuedCompletionStatus方法处。<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"> Iocp start() {</span><br><span class="line"> startThreads(new EventHandlerTask());</span><br><span class="line"> return this;</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> private class EventHandlerTask implements Runnable {</span><br><span class="line"> public void run() {</span><br><span class="line">。。。</span><br><span class="line"> try {</span><br><span class="line"> for (;;) {</span><br><span class="line"> </span><br><span class="line"> try {</span><br><span class="line"> //这里会阻塞，有iopc完成时间会唤醒</span><br><span class="line"> getQueuedCompletionStatus(port, ioResult);</span><br><span class="line"> } catch (IOException x) {</span><br><span class="line"> // should not happen</span><br><span class="line"> x.printStackTrace();</span><br><span class="line"> return;</span><br><span class="line"> }</span><br><span class="line">。。。</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure></p><p>我们用客户端发起一个连接，阻塞的这行就会被唤醒，跳到下一行<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br></pre></td><td class="code"><pre><span class="line"> // handle wakeup to execute task or shutdown</span><br><span class="line"> if (ioResult.completionKey() == 0 &&</span><br><span class="line"> ioResult.overlapped() == 0L)</span><br><span class="line"> {</span><br><span class="line"> Runnable task = pollTask();</span><br><span class="line"> if (task == null) {</span><br><span class="line"> // shutdown request</span><br><span class="line"> return;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // run task</span><br><span class="line"> // (if error/exception then replace thread)</span><br><span class="line"> replaceMe = true;</span><br><span class="line"> task.run();</span><br><span class="line"> continue;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // map key to channel</span><br><span class="line"> OverlappedChannel ch = null;</span><br><span class="line"> keyToChannelLock.readLock().lock();</span><br><span class="line"> try {</span><br><span class="line"> //这里根据completionKey找到channel，这个key就是前面我们关联iocp时传入的，现在有时间了，iocp给返回了。</span><br><span class="line"> ch = keyToChannel.get(ioResult.completionKey());</span><br><span class="line"> if (ch == null) {</span><br><span class="line"> checkIfStale(ioResult.overlapped());</span><br><span class="line"> continue;</span><br><span class="line"> }</span><br><span class="line"> } finally {</span><br><span class="line"> keyToChannelLock.readLock().unlock();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> //根据overlapped找到关联的对象。这个overlapped是我们在accept0里面放进去的。</span><br><span class="line"> PendingFuture<?,?> result = ch.getByOverlapped(ioResult.overlapped());</span><br><span class="line"> if (result == null) {</span><br><span class="line"> // we get here if the OVERLAPPED structure is associated</span><br><span class="line"> // with an I/O operation on a channel that was closed</span><br><span class="line"> // but the I/O operation event wasn't read in a timely</span><br><span class="line"> // manner. Alternatively, it may be related to a</span><br><span class="line"> // tryLock operation as the OVERLAPPED structures for</span><br><span class="line"> // these operations are not in the I/O cache.</span><br><span class="line"> checkIfStale(ioResult.overlapped());</span><br><span class="line"> continue;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // synchronize on result in case I/O completed immediately</span><br><span class="line"> // and was handled by initiator</span><br><span class="line"> synchronized (result) {</span><br><span class="line"> if (result.isDone()) {</span><br><span class="line"> continue;</span><br><span class="line"> }</span><br><span class="line"> // not handled by initiator</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // invoke I/O result handler</span><br><span class="line"> int error = ioResult.error();</span><br><span class="line"> //获取ResultHandler，实际上获取的是AcceptTask</span><br><span class="line"> ResultHandler， rh = (ResultHandler)result.getContext();</span><br><span class="line"> replaceMe = true; // (if error/exception then replace thread)</span><br><span class="line"> if (error == 0) {</span><br><span class="line"> //调用AcceptTask的complete方法，里面调用回调函数</span><br><span class="line"> rh.completed(ioResult.bytesTransferred(), canInvokeDirect);</span><br><span class="line"> } else {</span><br><span class="line"> rh.failed(error, translateErrorToIOException(error));</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>根据以上代码中的注释，我们基本上搞清楚了，如何accept一个请求后如何被唤醒的。总结下，主要是两个key，一个是将serverSocketChannel注册到Iocp中的CompletionKey，另一个是在AccetpEx函数中注册的overlapped。在java内存中用hashmap缓存key与对象关系。然后我们再看看回调函数的执行：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"> @Override</span><br><span class="line"> public void completed(int bytesTransferred, boolean canInvokeDirect) {</span><br><span class="line">。。。</span><br><span class="line"> //result是一个Future对象，设置result，get的地方会唤醒返回。</span><br><span class="line"> result.setResult(channel);</span><br><span class="line">。。。</span><br><span class="line"> // 调用回调的handler，Invoker是一个工具类，将调用进行了封装</span><br><span class="line"> Invoker.invokeIndirectly(result);</span><br><span class="line"> }</span><br></pre></td></tr></table></figure></p><p>Invoker内部代码逻辑比较简单，不再这里描述了。 </p><p>到这里，整个accept的过程就分析完了。</p><h2 id="异步读取数据"><a href="#异步读取数据" class="headerlink" title="异步读取数据"></a>异步读取数据</h2><p>下面我们继续分析，是如何异步读取数据的。</p><h3 id="回到demo中的accept的回调函数completed"><a href="#回到demo中的accept的回调函数completed" class="headerlink" title="回到demo中的accept的回调函数completed"></a>回到demo中的accept的回调函数completed</h3><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"> public void completed(AsynchronousSocketChannel channel, Object attachment) {</span><br><span class="line"> //这里得到一个channel，在这个channel上读取数据</span><br><span class="line"> ByteBuffer readBuff = ByteBuffer.allocate(1024);</span><br><span class="line"> try {</span><br><span class="line"> //如果没有数据可以读取</span><br><span class="line"> channel.read(readBuff, readBuff, new CompletionHandler<Integer, ByteBuffer>() {</span><br><span class="line">。。。。。。。</span><br><span class="line"> });</span><br><span class="line"> } catch (Exception e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> } finally {</span><br><span class="line"> //继续接收其他的客户端连接，如果不加这一行，只能连接一个客户端</span><br><span class="line"> server.accept(null, this);</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure><p>我们跟到channel.read内部：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br><span class="line">117</span><br><span class="line">118</span><br><span class="line">119</span><br><span class="line">120</span><br><span class="line">121</span><br><span class="line">122</span><br><span class="line">123</span><br><span class="line">124</span><br><span class="line">125</span><br><span class="line">126</span><br><span class="line">127</span><br><span class="line">128</span><br><span class="line">129</span><br><span class="line">130</span><br><span class="line">131</span><br><span class="line">132</span><br><span class="line">133</span><br><span class="line">134</span><br><span class="line">135</span><br><span class="line">136</span><br><span class="line">137</span><br><span class="line">138</span><br><span class="line">139</span><br><span class="line">140</span><br><span class="line">141</span><br></pre></td><td class="code"><pre><span class="line"> //AsynchronousSocketChannel</span><br><span class="line"> @Override</span><br><span class="line"> public final <A> void read(ByteBuffer dst,</span><br><span class="line"> A attachment,</span><br><span class="line"> CompletionHandler<Integer,? super A> handler)</span><br><span class="line"> {</span><br><span class="line"> read(dst, 0L, TimeUnit.MILLISECONDS, attachment, handler);</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> //AsynchronousSocketChannelImpl </span><br><span class="line"> @Override</span><br><span class="line"> public final <A> void read(ByteBuffer dst,</span><br><span class="line"> long timeout,</span><br><span class="line"> TimeUnit unit,</span><br><span class="line"> A attachment,</span><br><span class="line"> CompletionHandler<Integer,? super A> handler)</span><br><span class="line"> {</span><br><span class="line"> if (handler == null)</span><br><span class="line"> throw new NullPointerException("'handler' is null");</span><br><span class="line"> if (dst.isReadOnly())</span><br><span class="line"> throw new IllegalArgumentException("Read-only buffer");</span><br><span class="line"> read(false, dst, null, timeout, unit, attachment, handler);</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> </span><br><span class="line"> private <V extends Number,A> Future<V> read(boolean isScatteringRead,</span><br><span class="line"> ByteBuffer dst,</span><br><span class="line"> ByteBuffer[] dsts,</span><br><span class="line"> long timeout,</span><br><span class="line"> TimeUnit unit,</span><br><span class="line"> A att,</span><br><span class="line"> CompletionHandler<V,? super A> handler)</span><br><span class="line"> {</span><br><span class="line">。。。</span><br><span class="line"> return implRead(isScatteringRead, dst, dsts, timeout, unit, att, handler);</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> //WindowsAsynchronousSocketChannelImpl </span><br><span class="line"> @Override</span><br><span class="line"> <V extends Number,A> Future<V> implRead(boolean isScatteringRead,</span><br><span class="line"> ByteBuffer dst,</span><br><span class="line"> ByteBuffer[] dsts,</span><br><span class="line"> long timeout,</span><br><span class="line"> TimeUnit unit,</span><br><span class="line"> A attachment,</span><br><span class="line"> CompletionHandler<V,? super A> handler)</span><br><span class="line"> {</span><br><span class="line"> // setup task</span><br><span class="line"> PendingFuture<V,A> result =</span><br><span class="line"> new PendingFuture<V,A>(this, handler, attachment);</span><br><span class="line"> ByteBuffer[] bufs;</span><br><span class="line"> if (isScatteringRead) {</span><br><span class="line"> bufs = dsts;</span><br><span class="line"> } else {</span><br><span class="line"> bufs = new ByteBuffer[1];</span><br><span class="line"> bufs[0] = dst;</span><br><span class="line"> }</span><br><span class="line"> //新建一个ReadTask</span><br><span class="line"> final ReadTask<V,A> readTask =</span><br><span class="line"> new ReadTask<V,A>(bufs, isScatteringRead, result);</span><br><span class="line"> result.setContext(readTask);</span><br><span class="line"></span><br><span class="line"> // schedule timeout</span><br><span class="line"> if (timeout > 0L) {</span><br><span class="line"> Future<?> timeoutTask = iocp.schedule(new Runnable() {</span><br><span class="line"> public void run() {</span><br><span class="line"> readTask.timeout();</span><br><span class="line"> }</span><br><span class="line"> }, timeout, unit);</span><br><span class="line"> result.setTimeoutTask(timeoutTask);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // initiate I/O</span><br><span class="line"> if (Iocp.supportsThreadAgnosticIo()) {</span><br><span class="line"> //这里执行这个readTask</span><br><span class="line"> readTask.run();</span><br><span class="line"> } else {</span><br><span class="line"> Invoker.invokeOnThreadInThreadPool(this, readTask);</span><br><span class="line"> }</span><br><span class="line"> return result;</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> //ReadTask执行 </span><br><span class="line"> @Override</span><br><span class="line"> @SuppressWarnings("unchecked")</span><br><span class="line"> public void run() {</span><br><span class="line"> long overlapped = 0L;</span><br><span class="line"> boolean prepared = false;</span><br><span class="line"> boolean pending = false;</span><br><span class="line"></span><br><span class="line"> try {</span><br><span class="line"> begin();</span><br><span class="line"></span><br><span class="line"> // substitute non-direct buffers</span><br><span class="line"> prepareBuffers();</span><br><span class="line"> prepared = true;</span><br><span class="line"></span><br><span class="line"> // 这里又是一个overlapped</span><br><span class="line"> overlapped = ioCache.add(result);</span><br><span class="line"></span><br><span class="line"> // 调用native方法执行read，跟前面accept类似，这个方法不阻塞</span><br><span class="line"> int n = read0(handle, numBufs, readBufferArray, overlapped);</span><br><span class="line"> if (n == IOStatus.UNAVAILABLE) {</span><br><span class="line"> // I/O is pending</span><br><span class="line"> pending = true;</span><br><span class="line"> return;</span><br><span class="line"> }</span><br><span class="line"> if (n == IOStatus.EOF) {</span><br><span class="line"> // input shutdown</span><br><span class="line"> enableReading();</span><br><span class="line"> if (scatteringRead) {</span><br><span class="line"> result.setResult((V)Long.valueOf(-1L));</span><br><span class="line"> } else {</span><br><span class="line"> result.setResult((V)Integer.valueOf(-1));</span><br><span class="line"> }</span><br><span class="line"> } else {</span><br><span class="line"> throw new InternalError("Read completed immediately");</span><br><span class="line"> }</span><br><span class="line"> } catch (Throwable x) {</span><br><span class="line"> // failed to initiate read</span><br><span class="line"> // reset read flag before releasing waiters</span><br><span class="line"> enableReading();</span><br><span class="line"> if (x instanceof ClosedChannelException)</span><br><span class="line"> x = new AsynchronousCloseException();</span><br><span class="line"> if (!(x instanceof IOException))</span><br><span class="line"> x = new IOException(x);</span><br><span class="line"> result.setFailure(x);</span><br><span class="line"> } finally {</span><br><span class="line"> // release resources if I/O not pending</span><br><span class="line"> if (!pending) {</span><br><span class="line"> if (overlapped != 0L)</span><br><span class="line"> ioCache.remove(overlapped);</span><br><span class="line"> if (prepared)</span><br><span class="line"> releaseBuffers();</span><br><span class="line"> }</span><br><span class="line"> end();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // invoke completion handler</span><br><span class="line"> Invoker.invoke(result);</span><br><span class="line"> }</span><br></pre></td></tr></table></figure></p><p>跟accept的过程很类似，同样是通过iocp模型实现异步的，我们看看native方法read0的实现：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br></pre></td><td class="code"><pre><span class="line">JNIEXPORT jint JNICALL</span><br><span class="line">Java_sun_nio_ch_WindowsAsynchronousSocketChannelImpl_read0(JNIEnv* env, jclass this,</span><br><span class="line"> jlong socket, jint count, jlong address, jlong ov)</span><br><span class="line">{</span><br><span class="line"> SOCKET s = (SOCKET) jlong_to_ptr(socket);</span><br><span class="line"> WSABUF* lpWsaBuf = (WSABUF*) jlong_to_ptr(address);</span><br><span class="line"> OVERLAPPED* lpOverlapped = (OVERLAPPED*) jlong_to_ptr(ov);</span><br><span class="line"> BOOL res;</span><br><span class="line"> DWORD flags = 0;</span><br><span class="line"></span><br><span class="line"> ZeroMemory((PVOID)lpOverlapped, sizeof(OVERLAPPED));</span><br><span class="line"> res = WSARecv(s,</span><br><span class="line"> lpWsaBuf,</span><br><span class="line"> (DWORD)count,</span><br><span class="line"> NULL,</span><br><span class="line"> &flags,</span><br><span class="line"> lpOverlapped,</span><br><span class="line"> NULL);</span><br><span class="line"></span><br><span class="line"> if (res == SOCKET_ERROR) {</span><br><span class="line"> int error = WSAGetLastError();</span><br><span class="line"> if (error == WSA_IO_PENDING) {</span><br><span class="line"> return IOS_UNAVAILABLE;</span><br><span class="line"> }</span><br><span class="line"> if (error == WSAESHUTDOWN) {</span><br><span class="line"> return IOS_EOF; // input shutdown</span><br><span class="line"> }</span><br><span class="line"> JNU_ThrowIOExceptionWithLastError(env, "WSARecv failed");</span><br><span class="line"> return IOS_THROWN;</span><br><span class="line"> }</span><br><span class="line"> return IOS_UNAVAILABLE;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>这里是调用windows的WSARecv方法负责注册接收数据的实现方式。有数据过来，iocp的getQueuedCompletionStatus会被唤醒，得到ioResult对象，再根据CompletionKey和overlapped得到channel和PendingFuture，然后调用这个PendingFuture中的回调函数。</p><h2 id="wirte-异步"><a href="#wirte-异步" class="headerlink" title="wirte 异步"></a>wirte 异步</h2><p>wirte异步就跟accept/read方式一样了，不再重述。</p><h2 id="附加"><a href="#附加" class="headerlink" title="附加"></a>附加</h2><p>根据我们以上分析，这里最核心的地方是iocp，其内部是有一个线程池，负责管理多个Channel，默认使用 ThreadPool.getDefault()得到这个线程池，也可以自定义这个线程池：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">AsynchronousChannelGroup threadGroup = AsynchronousChannelGroup.withThreadPool((ExecutorService) getExecutor());</span><br><span class="line">serverSock = AsynchronousServerSocketChannel.open(threadGroup);</span><br></pre></td></tr></table></figure></p><h1 id="linux实现"><a href="#linux实现" class="headerlink" title="linux实现"></a>linux实现</h1><p>打开linux源代码，找到DefaultAsynchronousChannelProvider.create，继续找到LinuxAsynchronousChannelProvider<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line">@Override</span><br><span class="line">public AsynchronousServerSocketChannel openAsynchronousServerSocketChannel(AsynchronousChannelGroup group)</span><br><span class="line"> throws IOException</span><br><span class="line">{</span><br><span class="line"> return new UnixAsynchronousServerSocketChannelImpl(toPort(group));</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">private Port toPort(AsynchronousChannelGroup group) throws IOException {</span><br><span class="line"> if (group == null) {</span><br><span class="line"> return defaultEventPort();</span><br><span class="line"> } else {</span><br><span class="line"> if (!(group instanceof EPollPort))</span><br><span class="line"> throw new IllegalChannelGroupException();</span><br><span class="line"> return (Port)group;</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">private EPollPort defaultEventPort() throws IOException {</span><br><span class="line"> if (defaultPort == null) {</span><br><span class="line"> synchronized (LinuxAsynchronousChannelProvider.class) {</span><br><span class="line"> if (defaultPort == null) {</span><br><span class="line"> defaultPort = new EPollPort(this, ThreadPool.getDefault()).start();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> return defaultPort;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>可以看到这里使用的是一个EPollPort，跟windows上的Iocp类似：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">final class EPollPort extends Port{。。。}</span><br><span class="line">abstract class Port extends AsynchronousChannelGroupImpl{。。。}</span><br></pre></td></tr></table></figure></p><p>EPollPort实际上也是一个AsynchronousChannelGroup。我们先看看UnixAsynchronousServerSocketChannelImpl<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"> @Override</span><br><span class="line"> Future<AsynchronousSocketChannel> implAccept(Object att,</span><br><span class="line"> CompletionHandler<AsynchronousSocketChannel,Object> handler)</span><br><span class="line"> {</span><br><span class="line">。。。</span><br><span class="line"> try {</span><br><span class="line"> begin();</span><br><span class="line"> //这里直接调用accept方法</span><br><span class="line"> int n = accept(this.fd, newfd, isaa);</span><br></pre></td></tr></table></figure></p><p>调用的是native方法：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">JNIEXPORT jint JNICALL</span><br><span class="line">Java_sun_nio_ch_UnixAsynchronousServerSocketChannelImpl_accept0(JNIEnv* env,</span><br><span class="line"> jobject this, jobject ssfdo, jobject newfdo, jobjectArray isaa)</span><br><span class="line">{</span><br><span class="line"> return Java_sun_nio_ch_ServerSocketChannelImpl_accept0(env, this,</span><br><span class="line"> ssfdo, newfdo, isaa);</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>找到Java_sun_nio_ch_ServerSocketChannelImpl_accept0在ServerSocketChannelImpl.c中：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br></pre></td><td class="code"><pre><span class="line">JNIEXPORT jint JNICALL</span><br><span class="line">Java_sun_nio_ch_ServerSocketChannelImpl_accept0(JNIEnv *env, jobject this,</span><br><span class="line"> jobject ssfdo, jobject newfdo,</span><br><span class="line"> jobjectArray isaa)</span><br><span class="line">{</span><br><span class="line"> jint ssfd = (*env)->GetIntField(env, ssfdo, fd_fdID);</span><br><span class="line"> jint newfd;</span><br><span class="line"> struct sockaddr *sa;</span><br><span class="line"> int alloc_len;</span><br><span class="line"> jobject remote_ia = 0;</span><br><span class="line"> jobject isa;</span><br><span class="line"> jint remote_port;</span><br><span class="line"></span><br><span class="line"> NET_AllocSockaddr(&sa, &alloc_len);</span><br><span class="line"> if (sa == NULL) {</span><br><span class="line"> JNU_ThrowOutOfMemoryError(env, NULL);</span><br><span class="line"> return IOS_THROWN;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> /*</span><br><span class="line"> * accept connection but ignore ECONNABORTED indicating that</span><br><span class="line"> * a connection was eagerly accepted but was reset before</span><br><span class="line"> * accept() was called.</span><br><span class="line"> */</span><br><span class="line"> for (;;) {</span><br><span class="line"> socklen_t sa_len = alloc_len;</span><br><span class="line"> newfd = accept(ssfd, sa, &sa_len);</span><br><span class="line"> if (newfd >= 0) {</span><br><span class="line"> break;</span><br><span class="line"> }</span><br><span class="line"> if (errno != ECONNABORTED) {</span><br><span class="line"> break;</span><br><span class="line"> }</span><br><span class="line"> /* ECONNABORTED => restart accept */</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> if (newfd < 0) {</span><br><span class="line"> free((void *)sa);</span><br><span class="line"> if (errno == EAGAIN)</span><br><span class="line"> return IOS_UNAVAILABLE;</span><br><span class="line"> if (errno == EINTR)</span><br><span class="line"> return IOS_INTERRUPTED;</span><br><span class="line"> JNU_ThrowIOExceptionWithLastError(env, "Accept failed");</span><br><span class="line"> return IOS_THROWN;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> (*env)->SetIntField(env, newfdo, fd_fdID, newfd);</span><br><span class="line"> remote_ia = NET_SockaddrToInetAddress(env, sa, (int *)&remote_port);</span><br><span class="line"> free((void *)sa);</span><br><span class="line"> CHECK_NULL_RETURN(remote_ia, IOS_THROWN);</span><br><span class="line"> isa = (*env)->NewObject(env, isa_class, isa_ctorID, remote_ia, remote_port);</span><br><span class="line"> CHECK_NULL_RETURN(isa, IOS_THROWN);</span><br><span class="line"> (*env)->SetObjectArrayElement(env, isaa, 0, isa);</span><br><span class="line"> return 1;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>这里有个循环，一直accept，accept到了才跳出去。linux环境没有搭建好，不好调试，先写到这里，下次有机会在linux中调试。</p><h2 id="Linux-kernel-AIO这个奇葩"><a href="#Linux-kernel-AIO这个奇葩" class="headerlink" title="Linux kernel AIO这个奇葩"></a>Linux kernel AIO这个奇葩</h2><p>有位技术牛人研究linux aio，写了一遍blog：<br><a href="http://www.wzxue.com/linux-kernel-aio%e8%bf%99%e4%b8%aa%e5%a5%87%e8%91%a9/" target="_blank" rel="noopener">Linux kernel AIO这个奇葩</a></p><p>这个blog打不开了，可以看csdn上的转发：<br><a href="https://blog.csdn.net/abcd1f2/article/details/47440087" target="_blank" rel="noopener">https://blog.csdn.net/abcd1f2/article/details/47440087</a></p><p>Linux AIO 早就被提上议程，目前比较知名的有 Glibc 的 AIO 与 Kernel Native AIO </p><ul><li>Glibc AIO: <a href="http://www.ibm.com/developerworks/linux/library/l-async/" target="_blank" rel="noopener">http://www.ibm.com/developerworks/linux/library/l-async/</a> </li><li>Kernel Native AIO: <a href="http://lse.sourceforge.net/io/aio.html" target="_blank" rel="noopener">http://lse.sourceforge.net/io/aio.html</a> </li></ul><p>在Glibc AIO 的实现中， 用多线程同步来模拟 异步IO ，以上述代码为例，它牵涉了3个线程， 主线程（23908）新建 一个线程（23909）来调用 阻塞的pread函数，当pread返回时，又创建了一个线程（23910）来执行我们预设的异步回调函数， 23909 等待23910结束返回，然后23909也结束执行.. </p><p>实际上，为了避免线程的频繁创建、销毁，当有多个请求时，Glibc AIO 会使用线程池，但以上原理是不会变的，尤其要注意的是：我们的回调函数是在一个单独线程中执行的. </p><p>Glibc AIO 广受非议，存在一些难以忍受的缺陷和bug，饱受诟病，是极不推荐使用的. </p><p>详见：<a href="http://davmac.org/davpage/linux/async-io.html" target="_blank" rel="noopener">http://davmac.org/davpage/linux/async-io.html</a> </p><blockquote><p>目前linux上的AIO还不成熟，不推荐使用，那么jdk在linux上的aio是如何实现的呢？我们上文分析到，其实不是使用的linux aio，还是通过epoll实现的。</p></blockquote><h1 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h1><ul><li>java异步，不高清楚里面的原理，很容易出错。我在编写本文demo时，就是没有对原理搞清楚，遇到好多问题。 </li><li>api看起来很简单，如果完全用异步，那就不简单了。比如客户端发送数据，我要使用一个CountDown才能发下一条，否则容易报错，因为底层一个channel不能同时发多份数据</li></ul>]]></content>
<summary type="html">
<h1 id="说明"><a href="#说明" class="headerlink" title="说明"></a>说明</h1><p>Java AIO就是Java作为对异步IO提供支持的NIO.2 ，Java NIO2 (JSR 203)定义了更多的 New I/O APIs， 提案2003提出，直到2011年才发布， 最终在JDK 7中才实现。</p>
<p>从编程模式上来看AIO相对于NIO的区别在于，NIO需要使用者线程不停的轮询IO对象，来确定是否有数据准备好可以读了，而AIO则是在数据准备好之后，才会通知数据使用者，这样使用者就不需要不停地轮询了。</p>
<p>当然AIO的异步特性并不是Java实现的伪异步，而是使用了系统底层API的支持，在Unix系统下，采用了epoll IO模型，而windows便是使用了IOCP模型。</p>
</summary>
<category term="java" scheme="http://along101.site/categories/java/"/>
<category term="java" scheme="http://along101.site/tags/java/"/>
<category term="socket" scheme="http://along101.site/tags/socket/"/>
<category term="aio" scheme="http://along101.site/tags/aio/"/>
</entry>
<entry>
<title>java nio socket 原理分析</title>
<link href="http://along101.site/2018/01/22/java-nio-socket/"/>
<id>http://along101.site/2018/01/22/java-nio-socket/</id>
<published>2018-01-22T17:05:57.000Z</published>
<updated>2018-07-20T03:10:04.405Z</updated>
<content type="html"><![CDATA[<h1 id="java-nio简介"><a href="#java-nio简介" class="headerlink" title="java nio简介"></a>java nio简介</h1><p>java.nio全称java non-blocking IO，是指jdk1.4 及以上版本里提供的新api（New IO） ，为所有的原始类型（boolean类型除外）提供缓存支持的数据容器，使用它可以提供非阻塞式的高伸缩性网络。</p><a id="more"></a><h1 id="使用demo"><a href="#使用demo" class="headerlink" title="使用demo"></a>使用demo</h1><h2 id="server端代码"><a href="#server端代码" class="headerlink" title="server端代码"></a>server端代码</h2><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br></pre></td><td class="code"><pre><span class="line">ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();</span><br><span class="line">serverSocketChannel.configureBlocking(false);</span><br><span class="line">serverSocketChannel.socket().bind(new InetSocketAddress(port));</span><br><span class="line"></span><br><span class="line">Selector selector = Selector.open();</span><br><span class="line">serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);</span><br><span class="line"></span><br><span class="line">while (true) {</span><br><span class="line"> selector.select();</span><br><span class="line"> Set<SelectionKey> selectionKeys = selector.selectedKeys();</span><br><span class="line"> System.out.println(selectionKeys.size());</span><br><span class="line"> Iterator<SelectionKey> iterator = selectionKeys.iterator();</span><br><span class="line"> while (iterator.hasNext()) {</span><br><span class="line"> SelectionKey selectionKey = iterator.next();</span><br><span class="line"> // 删除已选的key 以防重复处理</span><br><span class="line"> iterator.remove();</span><br><span class="line"> if (selectionKey.isAcceptable()) {//如果有客户端连接进来</span><br><span class="line"> // 先拿到这个SelectionKey里面的ServerSocketChannel。</span><br><span class="line"> ServerSocketChannel serverSocketChannel1 = (ServerSocketChannel) selectionKey.channel();</span><br><span class="line"> // 获得和客户端连接的通道</span><br><span class="line"> SocketChannel socketChannel = serverSocketChannel1.accept();</span><br><span class="line"> socketChannel.configureBlocking(false);//将此通道设置为非阻塞</span><br><span class="line"></span><br><span class="line"> //为了接收客户端发送过来的数据，需要将此通道绑定到选择器上，并为该通道注册读事件</span><br><span class="line"> socketChannel.register(selector, SelectionKey.OP_READ);</span><br><span class="line"> } else if (selectionKey.isReadable()) {//客户端发送数据过来了</span><br><span class="line"> //先拿到这个SelectionKey里面的SocketChannel。</span><br><span class="line"> SocketChannel socketChannel = (SocketChannel) selectionKey.channel();</span><br><span class="line"> </span><br><span class="line"> ByteBuffer buf = ByteBuffer.allocate(100);</span><br><span class="line"> try {</span><br><span class="line"> if (socketChannel.read(buf) <= 0) {</span><br><span class="line"> return;</span><br><span class="line"> }</span><br><span class="line"> byte[] receivedData = buf.array();</span><br><span class="line"> String msg = new String(receivedData).trim();</span><br><span class="line"> System.out.println("receivedData：" + msg);</span><br><span class="line"> buf.clear();</span><br><span class="line"> socketChannel.write(ByteBuffer.wrap("收到信息!!!".getBytes()));</span><br><span class="line"> } catch (Exception e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h2 id="client端代码"><a href="#client端代码" class="headerlink" title="client端代码"></a>client端代码</h2><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br></pre></td><td class="code"><pre><span class="line">socketChannel = SocketChannel.open(new InetSocketAddress(this.host, this.port));</span><br><span class="line">socketChannel.configureBlocking(false);</span><br><span class="line"></span><br><span class="line">// 打开并注册选择器到信道</span><br><span class="line">Selector selector = Selector.open();</span><br><span class="line">socketChannel.register(selector, SelectionKey.OP_READ);</span><br><span class="line"></span><br><span class="line"> while (true) {</span><br><span class="line"> try {</span><br><span class="line"> selector.select();</span><br><span class="line"> Set<SelectionKey> set = selector.selectedKeys();</span><br><span class="line"> Iterator<SelectionKey> ite = set.iterator();</span><br><span class="line"></span><br><span class="line"> while (ite.hasNext()) {</span><br><span class="line"> SelectionKey selectionKey = ite.next();</span><br><span class="line"> ite.remove(); //删除已选的key,以防重复处理</span><br><span class="line"> if (selectionKey.isConnectable()) {//看是否有连接发生</span><br><span class="line"> SocketChannel socketChannel = (SocketChannel) selectionKey.channel();</span><br><span class="line"> //如果正在连接，则完成连接</span><br><span class="line"> if (socketChannel.isConnectionPending()) {</span><br><span class="line"> socketChannel.finishConnect();</span><br><span class="line"> }</span><br><span class="line"> socketChannel.configureBlocking(false);//设置为非阻塞模式</span><br><span class="line"> //给服务器端发送数据</span><br><span class="line"> System.out.println("客户端连接上了服务器端。。。。");</span><br><span class="line"> //为了接收来自服务器端的数据，将此通道注册到选择器中</span><br><span class="line"> socketChannel.register(selector, SelectionKey.OP_READ);</span><br><span class="line"> } else if (selectionKey.isReadable()) {</span><br><span class="line"> SocketChannel socketChannel = (SocketChannel) selectionKey.channel();</span><br><span class="line"> //接收来自于服务器端发送过来的数据</span><br><span class="line"> ByteBuffer buf = ByteBuffer.allocate(1024);</span><br><span class="line"> socketChannel.read(buf);</span><br><span class="line"> byte[] receiveData = buf.array();</span><br><span class="line"> String msg = new String(receiveData).trim();</span><br><span class="line"> System.out.println("接收来自服务器端的数据为：" + msg);</span><br><span class="line"> buf.clear();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> } catch (Exception e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure><h1 id="java-nio与io编程区别"><a href="#java-nio与io编程区别" class="headerlink" title="java nio与io编程区别"></a>java nio与io编程区别</h1><ul><li>io是基于流stream编程的，流没有读完或者写完，线程会阻塞</li><li>nio是基于缓冲区编程的，通过selector获取准备好的channel，从channel中获取数据到缓冲区，然后处理缓冲区数据。从select获取准备好的channel是一种通知机制。</li></ul><p>基于流编程是一个线程将流处理完，处理起来比较简单，但是向网络编程这种，多个连接的数据传输，就会多个线程，线程多就会增加线程切换带来的性能损耗。</p><p>基于nio的网络编程，使用一个selector来管理这些连接，当有事件发生时再处理。可以通过与cpu核心数相同大小的线程池来处理事件，这样就会减少线程切换。但是带来更加复杂的编程逻辑，因为缓冲区有大小限制，需要自行处理大数据传输缓冲区数据的拼接。</p><p>简单的说，selector的原理是使用一个selector来管理多个socket，当socket上有事件发生是，selector会把这个socket找出来，进行io处理。</p><p>用一张图，简单的描述io 和 nio区别</p><p><img src="/2018/01/22/java-nio-socket/1.png" alt=""></p><h1 id="java-nio-socket-selector模型原理"><a href="#java-nio-socket-selector模型原理" class="headerlink" title="java nio socket selector模型原理"></a>java nio socket selector模型原理</h1><p>要使用selector模型，需要将channel注册到selector上，服务端和客户端注册方式分别为：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);</span><br><span class="line">socketChannel.register(selector, SelectionKey.OP_READ);</span><br></pre></td></tr></table></figure></p><p><code>register</code>方法有两个重载的方法，返回一个<code>SelectionKey</code><br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">public final SelectionKey register(Selector sel, int ops)</span><br><span class="line">public abstract SelectionKey register(Selector sel, int ops, Object att)</span><br></pre></td></tr></table></figure></p><p>第二个方法多一个att参数，可以注册时增加一个附加的对象，用返回的<code>SelectionKey</code>可以设置这个att，注意这个att，非常有用，可以放需要的任意对象。</p><p>注册得到的这个<code>SelectionKey</code>是selector模型中的关键，我们看看SelectionKeyImpl的源代码<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">public class SelectionKeyImpl extends AbstractSelectionKey {</span><br><span class="line"> final SelChImpl channel;</span><br><span class="line"> public final SelectorImpl selector;</span><br><span class="line"> private int index;</span><br><span class="line"> private volatile int interestOps;</span><br><span class="line"> private int readyOps;</span><br><span class="line">。。。</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><ul><li><code>SelectorImpl</code> selector是所注册的选择器</li><li><code>interestOps</code>是所关心的操作事件集合，是一个int类型，使用二进制的位来组合不同时间集合</li><li><code>readyOps</code>是准备好的操作事件</li></ul><p>在channel上有四种：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">public static final int OP_READ = 1 << 0;//可读</span><br><span class="line">public static final int OP_WRITE = 1 << 2;//可写</span><br><span class="line">public static final int OP_CONNECT = 1 << 3;//准备好连接</span><br><span class="line">public static final int OP_ACCEPT = 1 << 4;//serverSoket接收连接</span><br></pre></td></tr></table></figure></p><p><code>SelectionKeyImpl</code> 的父类<code>SelectionKey</code>有一个属性<code>attachment</code> ，就是前文我们提到的注册时可以传入的对象。<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">private volatile Object attachment = null;</span><br></pre></td></tr></table></figure></p><p><code>SelectionKey</code>还提供两个方法<code>public final Object attach(Object ob)</code>和<code>public final Object attachment()</code>，或可以设置和获取<code>attachment</code>。</p><p><code>SelectionKeyImpl</code> 的属性channel是<code>SelChImpl</code>类型，是所有<code>Selectable Channel</code>的接口</p><p><img src="/2018/01/22/java-nio-socket/2.png" alt=""></p><p><code>SelectionKeyImpl</code>是一个接口，源代码如下：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">public interface SelChImpl extends Channel {</span><br><span class="line"> FileDescriptor getFD();</span><br><span class="line"> int getFDVal();</span><br><span class="line"> boolean translateAndUpdateReadyOps(int var1, SelectionKeyImpl var2);</span><br><span class="line"> boolean translateAndSetReadyOps(int var1, SelectionKeyImpl var2);</span><br><span class="line"> void translateAndSetInterestOps(int var1, SelectionKeyImpl var2);</span><br><span class="line"> int validOps();</span><br><span class="line"> void kill() throws IOException;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>在看看实现类<code>SocketChannel</code>的源代码：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line">class SocketChannelImpl extends SocketChannel implements SelChImpl {</span><br><span class="line"> private static NativeDispatcher nd;</span><br><span class="line"> private final FileDescriptor fd;</span><br><span class="line"> private final int fdVal;</span><br><span class="line"> private volatile long readerThread = 0L;</span><br><span class="line"> private volatile long writerThread = 0L;</span><br><span class="line"> private final Object readLock = new Object();</span><br><span class="line"> private final Object writeLock = new Object();</span><br><span class="line"> private final Object stateLock = new Object();</span><br><span class="line"> private boolean isReuseAddress;</span><br><span class="line"> private static final int ST_UNINITIALIZED = -1;</span><br><span class="line"> private static final int ST_UNCONNECTED = 0;</span><br><span class="line"> private static final int ST_PENDING = 1;</span><br><span class="line"> private static final int ST_CONNECTED = 2;</span><br><span class="line"> private static final int ST_KILLPENDING = 3;</span><br><span class="line"> private static final int ST_KILLED = 4;</span><br><span class="line"> private int state = -1;</span><br><span class="line"> private InetSocketAddress localAddress;</span><br><span class="line"> private InetSocketAddress remoteAddress;</span><br><span class="line"> private boolean isInputOpen = true;</span><br><span class="line"> private boolean isOutputOpen = true;</span><br><span class="line"> private boolean readyToConnect = false;</span><br><span class="line"> private Socket socket;</span><br><span class="line">。。。</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>这里有个很重要的属性，<code>FileDescriptor</code> fd，就是操作系统对socket的文件描述符，可以再看看<code>SocketImpl</code>的源代码，也有个<code>FileDescriptor</code> fd属性，这里是同一个。</p><p>文件描述符是一个简单的整数，用以标明每一个被进程所打开的文件和socket。可以理解为一个数组的索引，数组里面放着文件和socket相关的信息。</p><p>了解了<code>SelectionKey</code>和<code>Channel</code>的结构，我们再来看看注册到selector的过程。channel注册到selector是调用的<code>AbstractSelectableChannel.register</code>方法：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><span class="line">public final SelectionKey register(Selector sel, int ops, Object att)</span><br><span class="line"> throws ClosedChannelException</span><br><span class="line">{</span><br><span class="line"> synchronized (regLock) {</span><br><span class="line"> //先校验</span><br><span class="line"> if (!isOpen())</span><br><span class="line"> throw new ClosedChannelException();</span><br><span class="line"> if ((ops & ~validOps()) != 0)</span><br><span class="line"> throw new IllegalArgumentException();</span><br><span class="line"> if (blocking)</span><br><span class="line"> throw new IllegalBlockingModeException();</span><br><span class="line"> //在本地keys数组中找SelectionKey，如果找到了，直接设置关心的操作和att对象</span><br><span class="line"> SelectionKey k = findKey(sel);</span><br><span class="line"> if (k != null) {</span><br><span class="line"> k.interestOps(ops);</span><br><span class="line"> k.attach(att);</span><br><span class="line"> }</span><br><span class="line"> //没有找到，新注册SelectionKey ，并放到本地数组中缓存</span><br><span class="line"> if (k == null) {</span><br><span class="line"> // New registration</span><br><span class="line"> synchronized (keyLock) {</span><br><span class="line"> if (!isOpen())</span><br><span class="line"> throw new ClosedChannelException();</span><br><span class="line"> k = ((AbstractSelector)sel).register(this, ops, att);</span><br><span class="line"> addKey(k);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> return k;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>新注册<code>SelectionKey</code> 是调用selector的<code>register</code>方法：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">protected final SelectionKey register(AbstractSelectableChannel var1, int var2, Object var3) {</span><br><span class="line"> if (!(var1 instanceof SelChImpl)) {</span><br><span class="line"> throw new IllegalSelectorException();</span><br><span class="line"> } else {</span><br><span class="line"> //新建一个SelectionKeyImpl ，传入channel，和seletecor，设置attachment，设置关心的操作</span><br><span class="line"> SelectionKeyImpl var4 = new SelectionKeyImpl((SelChImpl)var1, this);</span><br><span class="line"> var4.attach(var3);</span><br><span class="line"> Set var5 = this.publicKeys;</span><br><span class="line"> synchronized(this.publicKeys) {</span><br><span class="line"> //调用SelectorImpl的抽象方法implRegister注册SelectionKeyImpl </span><br><span class="line"> this.implRegister(var4);</span><br><span class="line"> }</span><br><span class="line"> var4.interestOps(var2);</span><br><span class="line"> return var4;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p><code>implRegister</code>根据操作系统有不同的实现。</p><h2 id="windows上的实现"><a href="#windows上的实现" class="headerlink" title="windows上的实现"></a>windows上的实现</h2><p>我们先看看windows下如何实现的。<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">SelectorImpl在windows下子类是WindowsSelectorImpl，implRegister方法代码如下：</span><br><span class="line"> protected void implRegister(SelectionKeyImpl var1) {</span><br><span class="line"> Object var2 = this.closeLock;</span><br><span class="line"> synchronized(this.closeLock) {</span><br><span class="line"> if (this.pollWrapper == null) {</span><br><span class="line"> throw new ClosedSelectorException();</span><br><span class="line"> } else {</span><br><span class="line"> this.growIfNeeded();</span><br><span class="line"> this.channelArray[this.totalChannels] = var1;</span><br><span class="line"> var1.setIndex(this.totalChannels);</span><br><span class="line"> this.fdMap.put(var1);</span><br><span class="line"> this.keys.add(var1);</span><br><span class="line"> this.pollWrapper.addEntry(this.totalChannels, var1);</span><br><span class="line"> ++this.totalChannels;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure></p><p>这里把<code>SelectionKey</code>加到<code>SelectorImpl</code>中的好多地方<code>channelArray</code>、<code>fdMap</code>、<code>keys</code>、<code>pollWrapper</code>。加到每个地方的作用，我们先不管，后面再看，反正是保存在属性里面了。有个问题，连接关闭了的话，什么时候释放呢？ 后面我们会分析到。</p><p>从<code>selector.select()</code>方法往里面跟，跟到<code>SelectorImpl</code>的：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">private int lockAndDoSelect(long var1) throws IOException</span><br></pre></td></tr></table></figure></p><p>再跟到<code>WindowsSelectorImpl</code>的<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line">protected int doSelect(long var1) throws IOException {</span><br><span class="line">。。。</span><br><span class="line"> //先处理注销的key，通过selector调用cancel方法注销selectionKey</span><br><span class="line"> this.timeout = var1;</span><br><span class="line"> this.processDeregisterQueue();</span><br><span class="line"> if (this.interruptTriggered) {</span><br><span class="line"> this.resetWakeupSocket();</span><br><span class="line"> return 0;</span><br><span class="line">。。。</span><br><span class="line"> try {</span><br><span class="line"> //这里阻塞住</span><br><span class="line"> this.subSelector.poll();</span><br><span class="line"> } catch (IOException var7) {</span><br><span class="line"> this.finishLock.setException(var7);</span><br><span class="line"> }</span><br><span class="line">。。。</span><br><span class="line"> this.finishLock.checkForException();</span><br><span class="line"> this.processDeregisterQueue();</span><br><span class="line"> //更新SelectedKeys</span><br><span class="line"> int var3 = this.updateSelectedKeys();</span><br><span class="line"> this.resetWakeupSocket();</span><br><span class="line"> return var3;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure></p><p>重要的两行代码是<code>this.subSelector.poll();</code>和 <code>this.updateSelectedKeys();</code></p><p>先看<code>subSelector.poll()</code>，跟到<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">private int poll() throws IOException {</span><br><span class="line"> return this.poll0(WindowsSelectorImpl.this.pollWrapper.pollArrayAddress, Math.min(WindowsSelectorImpl.this.totalChannels, 1024), this.readFds, this.writeFds, this.exceptFds, WindowsSelectorImpl.this.timeout);</span><br><span class="line">}</span><br><span class="line">private native int poll0(long var1, int var3, int[] var4, int[] var5, int[] var6, long var7);</span><br></pre></td></tr></table></figure></p><p>这里<code>poll0</code>是一个native方法，再往下跟就需要看jdk的源代码了。</p><p>简单的解释下，这里用到了<code>pollWrapper</code>，我们回头看看之前注册的代码<code>this.pollWrapper.addEntry(this.totalChannels, var1);</code>这里面实际上是将<code>SelectionKey</code>的fd值放在<code>pollWrapper</code>内部的数组中，可参考<code>PollArrayWrapper</code>的代码。</p><p><code>poll0()</code>方法第一个参数为fd开始的地址，第二个是fd数量，后面三个fd数组分别是：保存发生read的FD，保存发生write的FD ，保存发生except（错误）的FD ，最后一个是超时时间。poll0（）会监听pollWrapper中的FD有没有数据进出，这会造成IO阻塞，直到有数据读写事件发生，然后将发生数据的分别保存在read/write/except数组中。</p><p>poll到发生事件的fd后，需要将找到这些fd对应的<code>SelectionKey</code>，通过<code>updateSelectedKeys</code>实现的：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">private int updateSelectedKeys() {</span><br><span class="line"> ++this.updateCount;</span><br><span class="line"> byte var1 = 0;</span><br><span class="line"> int var4 = var1 + this.subSelector.processSelectedKeys(this.updateCount);</span><br><span class="line"> WindowsSelectorImpl.SelectThread var3;</span><br><span class="line"> for(Iterator var2 = this.threads.iterator(); var2.hasNext(); var4 += var3.subSelector.processSelectedKeys(this.updateCount)) {</span><br><span class="line"> var3 = (WindowsSelectorImpl.SelectThread)var2.next();</span><br><span class="line"> }</span><br><span class="line"> return var4;</span><br><span class="line">}</span><br><span class="line"> private int processSelectedKeys(long var1) {</span><br><span class="line"> byte var3 = 0;</span><br><span class="line"> int var4 = var3 + this.processFDSet(var1, this.readFds, Net.POLLIN, false);</span><br><span class="line"> var4 += this.processFDSet(var1, this.writeFds, Net.POLLCONN | Net.POLLOUT, false);</span><br><span class="line"> var4 += this.processFDSet(var1, this.exceptFds, Net.POLLIN | Net.POLLCONN | Net.POLLOUT, true);</span><br><span class="line"> return var4;</span><br><span class="line"> }</span><br></pre></td></tr></table></figure></p><p>在看看<code>processFDSet</code>方法：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">private int processFDSet(long var1, int[] var3, int var4, boolean var5) {</span><br><span class="line"> 。。。</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>代码有点多，主要是根据前面保存三类fd数组找出<code>selectionKey</code>，加到<code>selectedKeys</code>中。前面注册的时候，将<code>SelectionKey</code>放到fdMap中，这里就从<code>fdMap</code>中根据fd找到<code>SelectionKey</code>。</p><p>后续通过<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">Set<SelectionKey> set = selector.selectedKeys();</span><br></pre></td></tr></table></figure></p><p>得到的<code>SelectionKey</code>集合就是这个这里加进来的，注意，我们遍历set时，拿出一个key，就要从set中删除掉，避免重复消费。</p><p>后面就是根据这个<code>SelectionKey</code>获取到<code>SocketChannel</code>，从<code>SocketChannel</code>中读取数据到<code>ByteBuffer</code>，处理业务逻辑。</p><p>到这里，我们就把channel注册到selector，到selector如何取到有事件发生的channel的过程分析完了，接下来我们看看通道关闭时，如何从selector中注销的。</p><p>从<code>socketChannel.close()</code>开始，找到<code>implCloseChannel()</code>，找到<code>AbstractSelectableChannel.implCloseChannel</code>：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">protected final void implCloseChannel() throws IOException {</span><br><span class="line"> implCloseSelectableChannel();</span><br><span class="line"> synchronized (keyLock) {</span><br><span class="line"> int count = (keys == null) ? 0 : keys.length;</span><br><span class="line"> for (int i = 0; i < count; i++) {</span><br><span class="line"> SelectionKey k = keys[i];</span><br><span class="line"> if (k != null)</span><br><span class="line"> k.cancel();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p><code>implCloseSelectableChannel()</code>先关闭chanel，然后逐个调用 <code>k.cancel()</code>取消<code>SelectionKey</code>，在往<code>k.cancel()</code>方法里面跟：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">public final void cancel() {</span><br><span class="line"> synchronized (this) {</span><br><span class="line"> if (valid) {</span><br><span class="line"> valid = false;</span><br><span class="line"> ((AbstractSelector)selector()).cancel(this);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>调用<code>selector</code>的<code>cancel</code>方法，再跟进去<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">void cancel(SelectionKey k) { </span><br><span class="line"> synchronized (cancelledKeys) {</span><br><span class="line"> cancelledKeys.add(k);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>将需要关闭的key加入到<code>cancelledKeys</code>集合中。啥时候处理这些关闭的key呢？先在<code>AbstractSelector</code>类中找<code>cancelledKeys</code>的用处，发现没有，再找子类<code>SelectorImpl</code>，发现：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">void processDeregisterQueue() throws IOException {</span><br><span class="line"> Set var1 = this.cancelledKeys();</span><br><span class="line"> synchronized(var1) {</span><br><span class="line"> if (!var1.isEmpty()) {</span><br><span class="line"> Iterator var3 = var1.iterator();</span><br><span class="line"> while(var3.hasNext()) {</span><br><span class="line"> SelectionKeyImpl var4 = (SelectionKeyImpl)var3.next();</span><br><span class="line"> try {</span><br><span class="line"> this.implDereg(var4);</span><br><span class="line"> } catch (SocketException var11) {</span><br><span class="line"> throw new IOException("Error deregistering key", var11);</span><br><span class="line"> } finally {</span><br><span class="line"> var3.remove();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>这里会调用<code>implDereg</code>实现注销<code>SelectionKey</code>，再找<code>processDeregisterQueue</code>方法被调用的地方，前文中我们已经分析过的代码，在<code>WindowsSelectorImpl.doSelect</code>里面会先调用<code>processDeregisterQueue</code>。</p><p>分析到这里，windows上的select的整个过程就完成了。</p><h2 id="linux上的实现"><a href="#linux上的实现" class="headerlink" title="linux上的实现"></a>linux上的实现</h2><p>下面我们分析下linux下是如何实现。</p><p>我们用jd-gui打开linux下的rt.jar，也可以直接在linux下用eclipse或者idea打开源代码。</p><p>从这行代码开始往下跟，看看获取的<code>Selector</code>是哪个类<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">Selector selector = Selector.open();</span><br></pre></td></tr></table></figure></p><p>跟到：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">public static Selector open() throws IOException {</span><br><span class="line"> return SelectorProvider.provider().openSelector();</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>默认情况下使用<code>DefaultSelectorProvider</code><br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">SelectorProvider.access$102(DefaultSelectorProvider.create());</span><br></pre></td></tr></table></figure></p><p>再跟进<code>sun.nio.ch.DefaultSelectorProvider.create</code>方法：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">public static SelectorProvider create()</span><br><span class="line">{</span><br><span class="line"> String str = (String)AccessController.doPrivileged(new GetPropertyAction("os.name"));</span><br><span class="line"> if (str.equals("SunOS")) {</span><br><span class="line"> return createProvider("sun.nio.ch.DevPollSelectorProvider");</span><br><span class="line"> }</span><br><span class="line"> if (str.equals("Linux")) {</span><br><span class="line"> return createProvider("sun.nio.ch.EPollSelectorProvider");</span><br><span class="line"> }</span><br><span class="line"> return new PollSelectorProvider();</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>可以看到，操作系统名字为Linux时，直接使用<code>EPollSelectorProvider</code>，实际上<code>epoll</code>是<code>linux</code>内核2.6之后出现的。</p><p><code>EPollSelectorProvider</code>创建<code>EPollSelectorImpl</code>。再看<code>EPollSelectorImpl</code>中注册<code>SelectionKey</code>的代码：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">protected void implRegister(SelectionKeyImpl paramSelectionKeyImpl)</span><br><span class="line">{</span><br><span class="line"> if (this.closed) {</span><br><span class="line"> throw new ClosedSelectorException();</span><br><span class="line"> }</span><br><span class="line"> SelChImpl localSelChImpl = paramSelectionKeyImpl.channel;</span><br><span class="line"> int i = Integer.valueOf(localSelChImpl.getFDVal()).intValue();</span><br><span class="line"> this.fdToKey.put(Integer.valueOf(i), paramSelectionKeyImpl);</span><br><span class="line"> this.pollWrapper.add(i);</span><br><span class="line"> this.keys.add(paramSelectionKeyImpl);</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>又是把<code>SelectionKey</code>加到<code>SelectorImpl</code>中，包括<code>fdToKey</code>、<code>pollWrapper</code>、<code>keys</code>。</p><p>我们先看看选择器是如何选择这些key的。<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line">protected int doSelect(long paramLong) throws IOException{</span><br><span class="line"> if (this.closed)</span><br><span class="line"> throw new ClosedSelectorException();</span><br><span class="line"> processDeregisterQueue();</span><br><span class="line"> try {</span><br><span class="line"> begin();</span><br><span class="line"> this.pollWrapper.poll(paramLong);</span><br><span class="line"> } finally {</span><br><span class="line"> end();</span><br><span class="line"> }</span><br><span class="line"> processDeregisterQueue();</span><br><span class="line"> int i = updateSelectedKeys();</span><br><span class="line"> if (this.pollWrapper.interrupted()){</span><br><span class="line"> this.pollWrapper.putEventOps(this.pollWrapper.interruptedIndex(), 0);</span><br><span class="line"> synchronized (this.interruptLock) {</span><br><span class="line"> this.pollWrapper.clearInterrupted();</span><br><span class="line"> IOUtil.drain(this.fd0);</span><br><span class="line"> this.interruptTriggered = false;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> return i;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>跟windows的代码有点类似，可以看到重点是调用了<code>this.pollWrapper.poll(paramLong);</code></p><p>再来看<code>EPollArrayWrapper.poll</code>方法：<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">int poll(long paramLong) throws IOException {</span><br><span class="line"> updateRegistrations();</span><br><span class="line"> this.updated = epollWait(this.pollArrayAddress, NUM_EPOLLEVENTS, paramLong, this.epfd);</span><br><span class="line"> for (int i = 0; i < this.updated; i++) {</span><br><span class="line"> if (getDescriptor(i) == this.incomingInterruptFD)</span><br><span class="line"> {</span><br><span class="line"> this.interruptedIndex = i;</span><br><span class="line"> this.interrupted = true;</span><br><span class="line"> break;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> return this.updated;</span><br><span class="line">}</span><br><span class="line">private native int epollWait(long paramLong1, int paramInt1, long paramLong2, int paramInt2) throws IOException;</span><br></pre></td></tr></table></figure></p><p>这里调用了本地的<code>epollWait</code>方法，大概解释下，第一个参数是拉出事件存放fd数组的地址，第二个是最大fd个数，第三个是超时时间，最后一个是epoll实例的fd，通过<code>epoll_create</code>创建的。</p><p><code>epollWait</code>方法会等待注册在epoll实例上的fd的事件，有事件发生，会将这些fd放在<code>pollArrayAddress</code>指向的数组中，返回发生事件的fd个数。</p><p>我们再回到<code>EPollSelectorImpl</code>的<code>doSelect</code>方法，poll到事件，将事件对应的fd放在数组里面，然后调用<code>updateSelectedKeys</code>方法，根据fd值找到<code>SelectionKey</code>值<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><span class="line">private int updateSelectedKeys()</span><br><span class="line">{</span><br><span class="line"> int i = this.pollWrapper.updated;</span><br><span class="line"> int j = 0;</span><br><span class="line"> for (int k = 0; k < i; k++)</span><br><span class="line"> {</span><br><span class="line"> int m = this.pollWrapper.getDescriptor(k);</span><br><span class="line"> SelectionKeyImpl localSelectionKeyImpl = (SelectionKeyImpl)this.fdToKey.get(Integer.valueOf(m));</span><br><span class="line"> if (localSelectionKeyImpl != null)</span><br><span class="line"> {</span><br><span class="line"> int n = this.pollWrapper.getEventOps(k);</span><br><span class="line"> if (this.selectedKeys.contains(localSelectionKeyImpl))</span><br><span class="line"> {</span><br><span class="line"> if (localSelectionKeyImpl.channel.translateAndSetReadyOps(n, localSelectionKeyImpl)) {</span><br><span class="line"> j++;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> else</span><br><span class="line"> {</span><br><span class="line"> localSelectionKeyImpl.channel.translateAndSetReadyOps(n, localSelectionKeyImpl);</span><br><span class="line"> if ((localSelectionKeyImpl.nioReadyOps() & localSelectionKeyImpl.nioInterestOps()) != 0)</span><br><span class="line"> {</span><br><span class="line"> this.selectedKeys.add(localSelectionKeyImpl);</span><br><span class="line"> j++;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> return j;</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p><p>代码有点多，看关键的<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">SelectionKeyImpl localSelectionKeyImpl = (SelectionKeyImpl)this.fdToKey.get(Integer.valueOf(m));</span><br></pre></td></tr></table></figure></p><p>从<code>fdToKey</code>中根据fd值拿到key，然后放到<code>selectedKeys</code>中。</p><p>到这里linux上的select实现模型也分析完了，注销方式跟windows上实现相同，不再描述。</p><h1 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h1><p>nio编程模型，主要是要搞清楚几个类之间的关系，<code>Selector</code>、<code>Channel</code>、<code>SelectionKey</code>，其中<code>SelectionKey</code>是<code>Selector</code>和<code>Channel</code>的纽带。</p><p><img src="/2018/01/22/java-nio-socket/3.png" alt=""></p><ul><li>一个<code>SelectableChannel</code>中包含多个<code>SelectKey</code>，是通过注册不同的<code>Selector</code>来实现的。</li><li>一个<code>Selector</code>中包含多个<code>SelectionKey</code>，每个<code>key</code>对应一个<code>channel</code></li><li>一个<code>SelectionKey</code>只包含一个<code>channel</code>和一个<code>selector</code></li></ul><p>也就是<code>channel</code>和<code>Selector</code>是多对多的关系，通过<code>SelectionKey</code>来关联。</p><p><code>SelectionKey</code>还可以设置一个<code>attachment</code>的附加对象，用于处理特定的业务逻辑。</p><h1 id="参考资源"><a href="#参考资源" class="headerlink" title="参考资源"></a>参考资源</h1><p><a href="https://www.cnblogs.com/Anker/p/3265058.html" target="_blank" rel="noopener">https://www.cnblogs.com/Anker/p/3265058.html</a> poll/select/epoll区别讲的很清晰</p>]]></content>
<summary type="html">
<h1 id="java-nio简介"><a href="#java-nio简介" class="headerlink" title="java nio简介"></a>java nio简介</h1><p>java.nio全称java non-blocking IO，是指jdk1.4 及以上版本里提供的新api（New IO） ，为所有的原始类型（boolean类型除外）提供缓存支持的数据容器，使用它可以提供非阻塞式的高伸缩性网络。</p>
</summary>
<category term="java" scheme="http://along101.site/categories/java/"/>
<category term="java" scheme="http://along101.site/tags/java/"/>
<category term="nio" scheme="http://along101.site/tags/nio/"/>
<category term="socket" scheme="http://along101.site/tags/socket/"/>
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