springaop的一个问题

在aop或者事务配置中都会使用AopConfigUtils，

static {
   APC_PRIORITY_LIST.add(InfrastructureAdvisorAutoProxyCreator.class);
   APC_PRIORITY_LIST.add(AspectJAwareAdvisorAutoProxyCreator.class);
   APC_PRIORITY_LIST.add(AnnotationAwareAspectJAutoProxyCreator.class);
}

<tx:annotation-driven transaction-manager="sqlTransactionManager" proxy-target-class="true" />

这个事务配置会注册InfrastructureAdvisorAutoProxyCreator

<aop:aspectj-autoproxy proxy-target-class="true" expose-proxy="true"/>

aop配置会注册AnnotationAwareAspectJAutoProxyCreator

但最终使用的是AnnotationAwareAspectJAutoProxyCreator，

注册的时候回进行优先级判断，优先级大的替换小的

private static BeanDefinition registerOrEscalateApcAsRequired(Class cls, BeanDefinitionRegistry registry, Object source) {
   Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
   if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) {
      BeanDefinition apcDefinition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);
      if (!cls.getName().equals(apcDefinition.getBeanClassName())) {
         int currentPriority = findPriorityForClass(apcDefinition.getBeanClassName());
         int requiredPriority = findPriorityForClass(cls);
         if (currentPriority             apcDefinition.setBeanClassName(cls.getName());
         }
      }
      return null;
   }
   RootBeanDefinition beanDefinition = new RootBeanDefinition(cls);
   beanDefinition.setSource(source);
   beanDefinition.getPropertyValues().add("order", Ordered.HIGHEST_PRECEDENCE);
   beanDefinition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
   registry.registerBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME, beanDefinition);
   return beanDefinition;
}

而优先级就是所在list的下标

private static int findPriorityForClass(String className) {
   for (int i = 0; i <APC_PRIORITY_LIST.size(); i++) {
      Class clazz = APC_PRIORITY_LIST.get(i);
      if (clazz.getName().equals(className)) {
         return i;
      }
   }
   throw new IllegalArgumentException(
         "Class name [" + className + "] is not a known auto-proxy creator class");
}

所以AnnotationAwareAspectJAutoProxyCreator优先级会比InfrastructureAdvisorAutoProxyCreator大，使用的是AnnotationAwareAspectJAutoProxyCreator。