Spring 源码阅读 70：基于 JDK 的 AOP 代理拦截器链执行（4）- 容易被忽略的 ExposeInvocationInterceptor

// org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator#findEligibleAdvisorsprotectedList<Advisor>findEligibleAdvisors(Class<?>beanClass, StringbeanName) {
List<Advisor>candidateAdvisors=findCandidateAdvisors();
List<Advisor>eligibleAdvisors=findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
extendAdvisors(eligibleAdvisors);
if (!eligibleAdvisors.isEmpty()) {
eligibleAdvisors=sortAdvisors(eligibleAdvisors);
   }
returneligibleAdvisors;
}

// org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator#extendAdvisorsprotectedvoidextendAdvisors(List<Advisor>candidateAdvisors) {
}

// org.springframework.aop.aspectj.autoproxy.AspectJAwareAdvisorAutoProxyCreator#extendAdvisors@OverrideprotectedvoidextendAdvisors(List<Advisor>candidateAdvisors) {
AspectJProxyUtils.makeAdvisorChainAspectJCapableIfNecessary(candidateAdvisors);
}

// org.springframework.aop.aspectj.AspectJProxyUtils#makeAdvisorChainAspectJCapableIfNecessarypublicstaticbooleanmakeAdvisorChainAspectJCapableIfNecessary(List<Advisor>advisors) {
// Don't add advisors to an empty list; may indicate that proxying is just not requiredif (!advisors.isEmpty()) {
booleanfoundAspectJAdvice=false;
for (Advisoradvisor : advisors) {
// Be careful not to get the Advice without a guard, as this might eagerly// instantiate a non-singleton AspectJ aspect...if (isAspectJAdvice(advisor)) {
foundAspectJAdvice=true;
break;
         }
      }
if (foundAspectJAdvice&&!advisors.contains(ExposeInvocationInterceptor.ADVISOR)) {
advisors.add(0, ExposeInvocationInterceptor.ADVISOR);
returntrue;
      }
   }
returnfalse;
}

publicfinalclassExposeInvocationInterceptorimplementsMethodInterceptor, PriorityOrdered, Serializable {
/** Singleton instance of this class. */publicstaticfinalExposeInvocationInterceptorINSTANCE=newExposeInvocationInterceptor();
/*** Singleton advisor for this class. Use in preference to INSTANCE when using* Spring AOP, as it prevents the need to create a new Advisor to wrap the instance.*/publicstaticfinalAdvisorADVISOR=newDefaultPointcutAdvisor(INSTANCE) {
@OverridepublicStringtoString() {
returnExposeInvocationInterceptor.class.getName() +".ADVISOR";
      }
   };
// 省略其他代码 }

// org.springframework.aop.interceptor.ExposeInvocationInterceptor#invoke@OverridepublicObjectinvoke(MethodInvocationmi) throwsThrowable {
MethodInvocationoldInvocation=invocation.get();
invocation.set(mi);
try {
returnmi.proceed();
   }
finally {
invocation.set(oldInvocation);
   }
}

privatestaticfinalThreadLocal<MethodInvocation>invocation=newNamedThreadLocal<>("Current AOP method invocation");