Support Spring RestClient as TransportClientFactory

docs/modules/ROOT/pages/spring-cloud-netflix.adoc

@@ -269,9 +269,9 @@ It is initialized in a `SmartLifecycle` (with `phase=0`), so the earliest you ca
 
 ==== Underlying HTTP clients
 
-`EurekaClient` uses either `RestTemplate`, `WebClient` or `JerseyClient` under the hood. In order to use the `EurekaClient`, you need to have one of the supported HTTP clients on your classpath.
+`EurekaClient` uses either `RestClient`, `RestTemplate`, `WebClient` or `JerseyClient` under the hood. In order to use the `EurekaClient`, you need to have one of the supported HTTP clients on your classpath.
 
-To use `RestTemplate`, add `spring-boot-starter-web` to your dependencies. To use `WebClient`, add `spring-boot-starter-webflux` to your dependencies. If both `RestTemplate` and `WebClient` are on the classpath when `eureka.client.webclient.enabled` is set to `true`, `WebClient` is used. Otherwise, `RestTemplate` is used.
+To use `RestTemplate` or `RestClient`, add `spring-boot-starter-web` to your dependencies. To use `WebClient`, add `spring-boot-starter-webflux` to your dependencies. If both `spring-boot-starter-web` and `spring-boot-starter-webflux` are included in the dependencies and the `eureka.client.webclient.enabled` is set to `true`, the `WebClient` will be used. On the other hand, if `eureka.client.restclient.enabled` is set to `true`, the `RestClient` will be used. Otherwise, the `RestTemplate` will be used.
 
 If you wish to use Jersey instead, you need to add the Jersey dependencies to your classpath.
 The following example shows the dependencies you need to add:

spring-cloud-netflix-eureka-client-tls-tests/src/test/java/org/springframework/cloud/netflix/eureka/RestTemplateEurekaClientTest.java

@@ -33,6 +33,7 @@
 import org.springframework.cloud.netflix.eureka.config.DiscoveryClientOptionalArgsConfiguration;
 import org.springframework.cloud.netflix.eureka.http.EurekaClientHttpRequestFactorySupplier;
 import org.springframework.cloud.netflix.eureka.http.RestTemplateDiscoveryClientOptionalArgs;
+import org.springframework.cloud.netflix.eureka.http.RestTemplateTransportClientFactories;
 import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
 import org.springframework.context.annotation.Bean;
 
@@ -82,6 +83,15 @@ public RestTemplateDiscoveryClientOptionalArgs forceRestTemplateDiscoveryClientO
 					eurekaClientHttpRequestFactorySupplier, new RestTemplateBuilderObjectProvider());
 		}
 
+		// Want to force reusing exactly the same bean as on production without excluding
+		// jersey from the classpath
+		@Bean
+		public RestTemplateTransportClientFactories forceRestTemplateTransportClientFactories(
+				DiscoveryClientOptionalArgsConfiguration configuration,
+				RestTemplateDiscoveryClientOptionalArgs discoveryClientOptionalArgs) {
+			return configuration.restTemplateTransportClientFactories(discoveryClientOptionalArgs);
+		}
+
 	}
 
 	@SpringBootConfiguration

spring-cloud-netflix-eureka-client/src/main/java/org/springframework/cloud/netflix/eureka/config/DiscoveryClientOptionalArgsConfiguration.java

@@ -25,7 +25,6 @@
 import org.apache.commons.logging.LogFactory;
 
 import org.springframework.beans.factory.ObjectProvider;
-import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
@@ -40,17 +39,21 @@
 import org.springframework.cloud.netflix.eureka.RestTemplateTimeoutProperties;
 import org.springframework.cloud.netflix.eureka.http.DefaultEurekaClientHttpRequestFactorySupplier;
 import org.springframework.cloud.netflix.eureka.http.EurekaClientHttpRequestFactorySupplier;
+import org.springframework.cloud.netflix.eureka.http.RestClientDiscoveryClientOptionalArgs;
+import org.springframework.cloud.netflix.eureka.http.RestClientTransportClientFactories;
 import org.springframework.cloud.netflix.eureka.http.RestTemplateDiscoveryClientOptionalArgs;
 import org.springframework.cloud.netflix.eureka.http.RestTemplateTransportClientFactories;
 import org.springframework.cloud.netflix.eureka.http.WebClientDiscoveryClientOptionalArgs;
 import org.springframework.cloud.netflix.eureka.http.WebClientTransportClientFactories;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.web.client.RestClient;
 import org.springframework.web.reactive.function.client.WebClient;
 
 /**
  * @author Daniel Lavoie
  * @author Armin Krezovic
+ * @author Wonchul Heo
  */
 @Configuration(proxyBeanMethods = false)
 @EnableConfigurationProperties(RestTemplateTimeoutProperties.class)
@@ -68,8 +71,6 @@ public TlsProperties tlsProperties() {
 	@ConditionalOnClass(name = "org.springframework.web.client.RestTemplate")
 	@ConditionalOnMissingClass("org.glassfish.jersey.client.JerseyClient")
 	@ConditionalOnMissingBean(value = { AbstractDiscoveryClientOptionalArgs.class }, search = SearchStrategy.CURRENT)
-	@ConditionalOnProperty(prefix = "eureka.client", name = "webclient.enabled", matchIfMissing = true,
-			havingValue = "false")
 	public RestTemplateDiscoveryClientOptionalArgs restTemplateDiscoveryClientOptionalArgs(TlsProperties tlsProperties,
 			EurekaClientHttpRequestFactorySupplier eurekaClientHttpRequestFactorySupplier,
 			ObjectProvider<RestTemplateBuilder> restTemplateBuilders) throws GeneralSecurityException, IOException {
@@ -84,8 +85,6 @@ public RestTemplateDiscoveryClientOptionalArgs restTemplateDiscoveryClientOption
 	@ConditionalOnClass(name = "org.springframework.web.client.RestTemplate")
 	@ConditionalOnMissingClass("org.glassfish.jersey.client.JerseyClient")
 	@ConditionalOnMissingBean(value = { TransportClientFactories.class }, search = SearchStrategy.CURRENT)
-	@ConditionalOnProperty(prefix = "eureka.client", name = "webclient.enabled", matchIfMissing = true,
-			havingValue = "false")
 	public RestTemplateTransportClientFactories restTemplateTransportClientFactories(
 			RestTemplateDiscoveryClientOptionalArgs optionalArgs) {
 		return new RestTemplateTransportClientFactories(optionalArgs);
@@ -125,14 +124,11 @@ static class DiscoveryClientOptionalArgsTlsConfiguration {
 	@ConditionalOnProperty(prefix = "eureka.client", name = "webclient.enabled", havingValue = "true")
 	protected static class WebClientConfiguration {
 
-		@Autowired
-		private TlsProperties tlsProperties;
-
 		@Bean
 		@ConditionalOnMissingBean(
 				value = { AbstractDiscoveryClientOptionalArgs.class, RestTemplateDiscoveryClientOptionalArgs.class },
 				search = SearchStrategy.CURRENT)
-		public WebClientDiscoveryClientOptionalArgs webClientDiscoveryClientOptionalArgs(
+		public WebClientDiscoveryClientOptionalArgs webClientDiscoveryClientOptionalArgs(TlsProperties tlsProperties,
 				ObjectProvider<WebClient.Builder> builder) throws GeneralSecurityException, IOException {
 			logger.info("Eureka HTTP Client uses WebClient.");
 			WebClientDiscoveryClientOptionalArgs result = new WebClientDiscoveryClientOptionalArgs(
@@ -164,4 +160,30 @@ public WebClientNotFoundConfiguration() {
 
 	}
 
+	@ConditionalOnMissingClass("org.glassfish.jersey.client.JerseyClient")
+	@ConditionalOnClass(name = "org.springframework.web.client.RestClient")
+	@ConditionalOnProperty(prefix = "eureka.client", name = "restclient.enabled", havingValue = "true")
+	protected static class RestClientConfiguration {
+
+		@Bean
+		@ConditionalOnMissingBean(value = { AbstractDiscoveryClientOptionalArgs.class },
+				search = SearchStrategy.CURRENT)
+		public RestClientDiscoveryClientOptionalArgs restClientDiscoveryClientOptionalArgs(TlsProperties tlsProperties,
+				ObjectProvider<RestClient.Builder> builder) throws GeneralSecurityException, IOException {
+			logger.info("Eureka HTTP Client uses RestClient.");
+			RestClientDiscoveryClientOptionalArgs result = new RestClientDiscoveryClientOptionalArgs(
+					builder::getIfAvailable);
+			setupTLS(result, tlsProperties);
+			return result;
+		}
+
+		@Bean
+		@ConditionalOnMissingBean(value = TransportClientFactories.class, search = SearchStrategy.CURRENT)
+		public RestClientTransportClientFactories restClientTransportClientFactories(
+				ObjectProvider<RestClient.Builder> builder) {
+			return new RestClientTransportClientFactories(builder::getIfAvailable);
+		}
+
+	}
+
 }

spring-cloud-netflix-eureka-client/src/main/java/org/springframework/cloud/netflix/eureka/config/EurekaConfigServerBootstrapConfiguration.java

@@ -27,6 +27,7 @@
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.autoconfigure.condition.SearchStrategy;
 import org.springframework.boot.autoconfigure.http.codec.CodecsAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.client.RestClientAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.reactive.function.client.WebClientAutoConfiguration;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.web.client.RestTemplateBuilder;
@@ -37,6 +38,8 @@
 import org.springframework.cloud.netflix.eureka.RestTemplateTimeoutProperties;
 import org.springframework.cloud.netflix.eureka.http.DefaultEurekaClientHttpRequestFactorySupplier;
 import org.springframework.cloud.netflix.eureka.http.EurekaClientHttpRequestFactorySupplier;
+import org.springframework.cloud.netflix.eureka.http.RestClientEurekaHttpClient;
+import org.springframework.cloud.netflix.eureka.http.RestClientTransportClientFactory;
 import org.springframework.cloud.netflix.eureka.http.RestTemplateEurekaHttpClient;
 import org.springframework.cloud.netflix.eureka.http.RestTemplateTransportClientFactory;
 import org.springframework.cloud.netflix.eureka.http.WebClientEurekaHttpClient;
@@ -46,6 +49,7 @@
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.env.Environment;
 import org.springframework.lang.Nullable;
+import org.springframework.web.client.RestClient;
 import org.springframework.web.reactive.function.client.WebClient;
 
 /**
@@ -54,6 +58,7 @@
  *
  * @author Dave Syer
  * @author Armin Krezovic
+ * @author Wonchul Heo
  */
 @ConditionalOnClass(ConfigServicePropertySourceLocator.class)
 @Conditional(EurekaConfigServerBootstrapConfiguration.EurekaConfigServerBootstrapCondition.class)
@@ -69,8 +74,6 @@ public EurekaClientConfigBean eurekaClientConfigBean() {
 
 	@Bean
 	@ConditionalOnMissingBean(EurekaHttpClient.class)
-	@ConditionalOnProperty(prefix = "eureka.client", name = "webclient.enabled", matchIfMissing = true,
-			havingValue = "false")
 	public RestTemplateEurekaHttpClient configDiscoveryRestTemplateEurekaHttpClient(EurekaClientConfigBean config,
 			Environment env, @Nullable TlsProperties properties,
 			EurekaClientHttpRequestFactorySupplier eurekaClientHttpRequestFactorySupplier,
@@ -109,6 +112,22 @@ public WebClientEurekaHttpClient configDiscoveryWebClientEurekaHttpClient(Eureka
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnClass(name = "org.springframework.web.client.RestClient")
+	@ConditionalOnProperty(prefix = "eureka.client", name = "restclient.enabled", havingValue = "true")
+	@ImportAutoConfiguration(RestClientAutoConfiguration.class)
+	protected static class RestClientConfiguration {
+
+		@Bean
+		@ConditionalOnMissingBean(EurekaHttpClient.class)
+		public RestClientEurekaHttpClient configDiscoveryRestClientEurekaHttpClient(EurekaClientConfigBean config,
+				ObjectProvider<RestClient.Builder> builder, Environment env) {
+			return (RestClientEurekaHttpClient) new RestClientTransportClientFactory(builder::getIfAvailable)
+					.newClient(HostnameBasedUrlRandomizer.randomEndpoint(config, env));
+		}
+
+	}
+
 	static class EurekaConfigServerBootstrapCondition extends AllNestedConditions {
 
 		EurekaConfigServerBootstrapCondition() {

spring-cloud-netflix-eureka-client/src/main/java/org/springframework/cloud/netflix/eureka/http/EurekaHttpClientUtils.java

@@ -0,0 +1,127 @@
+/*
+ * Copyright 2017-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.netflix.eureka.http;
+
+import java.net.URI;
+import java.net.URISyntaxException;
+
+import com.fasterxml.jackson.databind.BeanDescription;
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.JsonSerializer;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies;
+import com.fasterxml.jackson.databind.SerializationConfig;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+import com.fasterxml.jackson.databind.ser.BeanSerializerModifier;
+import com.fasterxml.jackson.databind.ser.std.BeanSerializerBase;
+import com.netflix.appinfo.InstanceInfo;
+import com.netflix.discovery.converters.jackson.mixin.ApplicationsJsonMixIn;
+import com.netflix.discovery.converters.jackson.mixin.InstanceInfoJsonMixIn;
+import com.netflix.discovery.converters.jackson.serializer.InstanceInfoJsonBeanSerializer;
+import com.netflix.discovery.shared.Applications;
+import com.netflix.discovery.shared.transport.EurekaHttpClient;
+
+import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
+import org.springframework.lang.Nullable;
+
+/**
+ * Utility class for dealing with {@link EurekaHttpClient}.
+ *
+ * @author Wonchul Heo
+ */
+final class EurekaHttpClientUtils {
+
+	private EurekaHttpClientUtils() {
+		throw new AssertionError("Must not instantiate constant utility class");
+	}
+
+	/**
+	 * Provides the serialization configurations required by the Eureka Server. JSON
+	 * content exchanged with eureka requires a root node matching the entity being
+	 * serialized or deserialized. Achieved with
+	 * {@link SerializationFeature#WRAP_ROOT_VALUE} and
+	 * {@link DeserializationFeature#UNWRAP_ROOT_VALUE}.
+	 * {@link PropertyNamingStrategies.SnakeCaseStrategy} is applied to the underlying
+	 * {@link ObjectMapper}.
+	 * @return a {@link MappingJackson2HttpMessageConverter} object
+	 */
+	static MappingJackson2HttpMessageConverter mappingJacksonHttpMessageConverter() {
+		final MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
+		converter.setObjectMapper(objectMapper());
+		return converter;
+	}
+
+	/**
+	 * Provides the serialization configurations required by the Eureka Server. JSON
+	 * content exchanged with eureka requires a root node matching the entity being
+	 * serialized or deserialized. Achieved with
+	 * {@link SerializationFeature#WRAP_ROOT_VALUE} and
+	 * {@link DeserializationFeature#UNWRAP_ROOT_VALUE}.
+	 * {@link PropertyNamingStrategies.SnakeCaseStrategy} is applied to the underlying
+	 * {@link ObjectMapper}.
+	 * @return a {@link ObjectMapper} object
+	 */
+	static ObjectMapper objectMapper() {
+		final ObjectMapper objectMapper = new ObjectMapper();
+		objectMapper.setPropertyNamingStrategy(PropertyNamingStrategies.SNAKE_CASE);
+
+		final SimpleModule jsonModule = new SimpleModule();
+		jsonModule.setSerializerModifier(createJsonSerializerModifier());
+		objectMapper.registerModule(jsonModule);
+
+		objectMapper.configure(SerializationFeature.WRAP_ROOT_VALUE, true);
+		objectMapper.configure(DeserializationFeature.UNWRAP_ROOT_VALUE, true);
+		objectMapper.addMixIn(Applications.class, ApplicationsJsonMixIn.class);
+		objectMapper.addMixIn(InstanceInfo.class, InstanceInfoJsonMixIn.class);
+
+		return objectMapper;
+	}
+
+	private static BeanSerializerModifier createJsonSerializerModifier() {
+		return new BeanSerializerModifier() {
+			@Override
+			public JsonSerializer<?> modifySerializer(SerializationConfig config, BeanDescription beanDesc,
+					JsonSerializer<?> serializer) {
+				if (beanDesc.getBeanClass().isAssignableFrom(InstanceInfo.class)) {
+					return new InstanceInfoJsonBeanSerializer((BeanSerializerBase) serializer, false);
+				}
+				return serializer;
+			}
+		};
+	}
+
+	@Nullable
+	static UserInfo extractUserInfo(String serviceUrl) {
+		try {
+			final URI serviceURI = new URI(serviceUrl);
+			if (serviceURI.getUserInfo() != null) {
+				final String[] credentials = serviceURI.getUserInfo().split(":");
+				if (credentials.length == 2) {
+					return new UserInfo(credentials[0], credentials[1]);
+				}
+			}
+		}
+		catch (URISyntaxException ignore) {
+		}
+		return null;
+	}
+
+	record UserInfo(String username, String password) {
+	}
+
+}

spring-cloud-netflix-eureka-client/src/main/java/org/springframework/cloud/netflix/eureka/http/NotFoundHttpResponse.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2017-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.netflix.eureka.http;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpStatusCode;
+import org.springframework.http.client.ClientHttpResponse;
+
+/**
+ * Response that ignores body, specifically for 404 errors.
+ *
+ * @author Wonchul Heo
+ */
+class NotFoundHttpResponse implements ClientHttpResponse {
+
+	private final ClientHttpResponse response;
+
+	NotFoundHttpResponse(ClientHttpResponse response) {
+		this.response = response;
+	}
+
+	@Override
+	public HttpStatusCode getStatusCode() throws IOException {
+		return response.getStatusCode();
+	}
+
+	@Override
+	public String getStatusText() throws IOException {
+		return response.getStatusText();
+	}
+
+	@Override
+	public void close() {
+		response.close();
+	}
+
+	@Override
+	public InputStream getBody() throws IOException {
+		// ignore body on 404 for heartbeat, see gh-4145
+		return null;
+	}
+
+	@Override
+	public HttpHeaders getHeaders() {
+		return response.getHeaders();
+	}
+
+}