16-Spring AOP源码分析-@EnableAspectJAutoProxy和AspectJAutoProxyRegistrar

@EnableAspectJAutoProxy

**2）我们看到在我们配置类上加入了@EnableAspectJAutoProxy,我们着重来分析一下这个东东给我容器中添加了什么组件？

**2.1)我们发现@EnableAspectJAutoProxy上标注了一个@Import注解，通过前面的学习我们知道@Import可以给我们容器****中添加组件

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(AspectJAutoProxyRegistrar.class)
public @interface EnableAspectJAutoProxy {

AspectJAutoProxyRegistrar

2.2)所以我们来分析AspectJAutoProxyRegistrar类是用来干什么的？

经过跟踪源代码我们发现,AspectJAutoProxyRegistrar实现了ImportBeanDefinitionRegistrar接口，我们以前学习过

凡是实现了*ImportBeanDefinitionRegistrar可以给我们容器中添加bean定义信息*

*作用:往容器中注册了一个名称叫org.springframework.aop.config.internalAutoProxyCreator*

​ *类型为AnnotationAwareAspectJAutoProxyCreator 注解的apsectj自动代理创建器*

class AspectJAutoProxyRegistrar implements ImportBeanDefinitionRegistrar {

	@Override
	public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        
        //往容器中注册对应的 aspectj注解自动代理创建器
		AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry);
        
		AnnotationAttributes enableAspectJAutoProxy =
				AnnotationConfigUtils.attributesFor(importingClassMetadata, EnableAspectJAutoProxy.class);
		if (enableAspectJAutoProxy.getBoolean("proxyTargetClass")) {
			AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);
		}
		if (enableAspectJAutoProxy.getBoolean("exposeProxy")) {
			AopConfigUtils.forceAutoProxyCreatorToExposeProxy(registry);
		}
	}

}

======================AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry);======================
	public static BeanDefinition registerAspectJAnnotationAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry) {
		return registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry, null);
	}
	
	//注册一个AnnotationAwareAspectJAutoProxyCreator（注解适配的切面自动创建器）
	public static BeanDefinition registerAspectJAnnotationAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry, Object source) {
		return registerOrEscalateApcAsRequired(AnnotationAwareAspectJAutoProxyCreator.class, registry, source);
	}

	private static BeanDefinition registerOrEscalateApcAsRequired(Class cls, BeanDefinitionRegistry registry, Object source) {
		Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
        
        //判断容器中有没有org.springframework.aop.config.internalAutoProxyCreator 名称的bean定义
		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 < requiredPriority) {
					apcDefinition.setBeanClassName(cls.getName());
				}
			}
			return null;
		}
        
        //容器中没有 那么就注册一个名称叫org.springframework.aop.config.internalAutoProxyCreator  类型是AnnotationAwareAspectJAutoProxyCreator的bean定义
		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;
	}