Fix memory leak on AOP Proxy class definition cache

[yokotaso]

Fix memory leak on AOP Proxy class definition cache.

How to reproduce

1. Like @Validated annotation with Request scope Controller like bellow

// Annnotation definition
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Controller
@Scope(WebApplicationContext.SCOPE_REQUEST)
@RequestMapping(method = { RequestMethod.GET, RequestMethod.HEAD })
@Transactional
@Validated
public @interface MyController {
}

@MyController
public class RootController {
    @ModelAttribute("requireJs")
    public boolean isRequireJs() {
        return true;
    }

    @RequestMapping("/search")
    public String search(
        Model model, 
        @RequestParam(value = "space", required = false) @Max(value=100) String space) {
        // ommit
    }
}

2. Aop class definition cache won't work well, therefore memory leak

Why

this bug is intruced by:

• https://github.com/spring-projects/spring-framework/pull/26017/files#diff-8b811560ae60c9f7937f0d378880f1b4366fa67ea7024db018931a26e3b449edL370-L376
• https://github.com/spring-projects/spring-framework/pull/26017/files#diff-dd90aa36a7221a652e04631ac19dcb6693a9c841e43a90d36cc3caa51121630eL945-L947

1. Because @Validated annotation added,
   AbstractAdvisingBeanPostProcessor#postProcessAfterInitialization add advice for @Validated

2. Before Improve AdvisedSupport.getAdvisors() #26017,
   cache in org.springframework.cglib.core.AbstractClassGenerator works well.
   Because org.springframework.aop.framework.AdvisedSupport#getConfigurationOnlyCopy
   copy org.springframework.aop.framework.AdvisedSupport#advisorsArray for create copy instance.

But after #26017,
use same reference of org.springframework.aop.framework.AdvisedSupport#advisors for
create copy instance. and this advitors field update by AbstractAdvisingBeanPostProcessor#postProcessAfterInitialization

3. When Create Aop class instance, try to reuse cache for class definition

Cache key is defined below code:

• org.springframework.cglib.proxy.Enhancer#createClass
• org.springframework.cglib.proxy.Enhancer#createHelper

org.springframework.cglib.proxy.Enhancer#filter is registered at
https://github.com/spring-projects/spring-framework/blob/main/spring-aop/src/main/java/org/springframework/aop/framework/CglibAopProxy.java#L201-L202

4. cache miss for class definition, memory leak happen
   At AbstractAdvisingBeanPostProcessor#postProcessAfterInitialization, advice object
   updated and therefore cache key is pollute, cache miss and memory leak happen.
   

So, When creating copy instance on org.springframework.aop.framework.AdvisedSupport#getConfigurationOnlyCopy,
It is good that create new instance of ArrayList and copy all advices.

This bug reported by @hikoma Thanks!

[sbrannen]

Thanks for the PR and the detailed report.

We'll look into it.

[sbrannen]

Related issues:

• Memory leak with CglibAopProxy$ProxyCallbackFilter #26266
• JVM Metaspace keeps growing with @RequestScope, AOP and @Validated because of proxying. #27395