何时以及如何创建 cglib 代理的组件实例

Question

I'd like to learn if there are some rules / conditions that a Spring component is wrapped (proxied) by CGLIB. For example, take this case:

@Component
public class TestComponent {
}

@Service
//@Transactional(rollbackFor = Throwable.class)
public class ProcessComponent {

    @Autowired
    private TestComponent testComponent;

    public void doSomething(int key) {
      // try to debug "testComponent" instance here ...
    }

}

If we let it like this and debug the testComponent field inside the method, then we'll see that it's not wrapped by CGLIB.

Now if we uncomment the @Transactional annotation and debug, we'll find that the instance is wrapped: it's of type ProcessComponent$$EnhancerByCGLIB$$14456 or something like that. It's clearly because Spring needs to create a proxy class to handle the transaction support.

But I'm wondering, is there any way that we can detect how and when does this wrapping happen? For example, some specific locations in Spring's source code to debug into to find more information; or some documentations on the rules of how they decide to create a proxy.

For your information, I need to know about this because I'm facing a situation where some component ( not @Transactional, above example is just for demonstrating purpose ) in my application suddenly becomes proxied (I found a revision a bit in the past where it is not). The most important issue is that this'll affect such components that also contain public final methods and another issue (also of importance) is that there must have been some unexpected changes in the design / structure of classes. For these kind of issues, of course we must try to find out what happened / who did the change that led to this etc...

One note is that we have just upgraded our application from Spring Boot 2.1.0RELEASE to 2.1.10RELEASE. And checking the code revision by revision up till now is not feasible, because there have been quite a lot of commits.

Any kind of help would be appreciated, thanks in advance.

Answer 1

You could debug into org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.getAdvicesAndAdvisorsForBean(Class, String, TargetSource). If any advisor is found, the bean will be proxied.

Answer 2

If you use a @Lookup method injection it will also proxy the component class.