Code for the Improve your legacy app with Spring talks.
There are several branches showing the migration from a Legacy Monolitic application to a well (or better) structured application which can be broken into different parts.
Shows the upgrade from Spring 2.0.8 to the 3.2.13 version of Spring. The 3.2 version is the last version to include a SimpleFormController and this would allow for a easier migration path. There is now the choice to either use the SimpleFormController albeight deprecated, or to switch to @Controller.
The JDK has been updated from 1.4 to 1.6 and the code remains unchanged.
Added an integration test for the UserServiceImpl to test the creation of the user, sending an email and synchronize with a remote system. With monolitic application services often do too much things and a unit test is in those case basically an integration test.
Use mocking/stub libraries to mimic services like SMTP, FTP etc.
Seperate the sending mail en synchronizing to seperate services which the UserServiceImpl simply delegates to. There is also need for change of the configuration as we now need to have a couple more dependencies injected into the UserServiceImpl.
The testcase remains untouched and still should give green bars indicating everything is still working.
The different services and accompining classes have been moved into different functional packages like nl.conspect.legacy.user and nl.conspect.legacy.mail.
The testcase is moved to a different package, but for the remainder remains untouched.
Introduce events to have even more loosely coupled components.
Now that everything is nicely structured we have the ability to move those different parts to indepedent applications. Here we move the mail service to a seperate application and interface with it throuhg Spring Remoting, Spring Integration using JMS with and without XML marshalling.
A question arose during the webinar regarding the migration of older SimpleFormController implementations to @Controller and @RequestMapping. The first step is to write a testcase for the controller(s) you want to migrate then one by one migrate your controllers to @Controller. This way you have a controlled migration path.
As soon as you migrated a full functional package to the new controllers you could think of moving it to an indepent service and use for instance Spring Boot to launch that part of your application.
Note: This means that during migration you are bound to the 2.x or 3.x versions of Spring as that includes the SimpleFormController, Spring 4.x and later don't contain that class anymore.