接上篇博客:Spring技术内幕3——Spring AOP原理（一）

Spring Aop最终转换成JdkDynamicAopProxy或者ObjenesisCglibAopProxy来作为入口对对象进行调用

 JdkDynamicAopProxy的入口是invoke函数，ObjenesisCglibAopProxy的入口是DynamicAdvisedInterceptor的intercept方法。其实最终都是转化成ReflectiveMethodInvocation的proceed方法。

我们接下来看proceed方法的源码：

public Object proceed() throws Throwable {		//	We start with an index of -1 and increment early.		if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {			return invokeJoinpoint();		}		Object interceptorOrInterceptionAdvice =				this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);		if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {			// Evaluate dynamic method matcher here: static part will already have			// been evaluated and found to match.			InterceptorAndDynamicMethodMatcher dm =					(InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;			if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) {				return dm.interceptor.invoke(this);			}			else {				// Dynamic matching failed.				// Skip this interceptor and invoke the next in the chain.				return proceed();			}		}		else {			// It's an interceptor, so we just invoke it: The pointcut will have			// been evaluated statically before this object was constructed.			return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);		}	}

     根据之前的拦截器链进行相关的匹配，我们这里可以看到，它是遍历了所有的interceptorsAndDynamicMethodMatchers，那么interceptorsAndDynamicMethodMatchers这个是哪里来的呢？我们继续回头看。

    我们在之前的配置中对ProxyFactoryBean配置了interceptorNames属性，我们在initializeAdvisorChain()初始化AdvisorChain链条的过程中，将interceptoeNames中相关的Bean对象作为Advisor注入到了

        AdvisedSupport的advisors的List集合中，我们知道ProxyFactoryBean也是AdvisedSupport的子类

因此在:

@Override	public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {		if (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) {			Class
     targetClass = config.getTargetClass();			if (targetClass == null) {				throw new AopConfigException("TargetSource cannot determine target class: " +						"Either an interface or a target is required for proxy creation.");			}			if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) {				return new JdkDynamicAopProxy(config);			}			return new ObjenesisCglibAopProxy(config);		}		else {			return new JdkDynamicAopProxy(config);		}	}

        这个方法中将ProxyBeanFactory已经注入了JdkDynamicAopProxy或者ObjenesisCglibAopProxy中，我们再回到CglibAopProxy或者JdkDynamicAopProxy这两个类中。

List

   由此可以看出这边的拦截链就是调用的ProxyFactoryBean中的getInterceptorsAndDynamicInterceptionAdvice方法，而又因为ProxyFactoryBean继承于AdvisedSupport类，因此最终调用的是

DefaultAdvisorChainFactory中的getInterceptorsAndDynamicInterceptionAdvice方法。

public List

    而config.getAdvisors().length则是ProxyFactoryBean中interceptorNames的配置的长度，我们继续往下看，可以看到这里使用了

       AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();

作为一个注册器，真正的注册器则是这个DefaultAdvisorAdapterRegistry，我们可以看到Spring中使用了很多的涉及模式，把真正的实现和接口分离了开来。

/**	 * Create a new DefaultAdvisorAdapterRegistry, registering well-known adapters.	 */	public DefaultAdvisorAdapterRegistry() {		registerAdvisorAdapter(new MethodBeforeAdviceAdapter());		registerAdvisorAdapter(new AfterReturningAdviceAdapter());		registerAdvisorAdapter(new ThrowsAdviceAdapter());	}@Override	public MethodInterceptor[] getInterceptors(Advisor advisor) throws UnknownAdviceTypeException {		List
    
      interceptors = new ArrayList
     
      (3);		Advice advice = advisor.getAdvice();		if (advice instanceof MethodInterceptor) {			interceptors.add((MethodInterceptor) advice);		}		for (AdvisorAdapter adapter : this.adapters) {			if (adapter.supportsAdvice(advice)) {				interceptors.add(adapter.getInterceptor(advisor));			}		}		if (interceptors.isEmpty()) {			throw new UnknownAdviceTypeException(advisor.getAdvice());		}		return interceptors.toArray(new MethodInterceptor[interceptors.size()]);	}
     
    

        我们从名称基本可以看出这里注册了MethodBeforeAdvice、AfterReturningAdvice、ThrowAdvice这三个Advice的适配器，我们来看一个具体的适配器的相关过程

MethodBeforeAdviceAdapter中adapter.getTnterceptor调用的是:

@Override	public boolean supportsAdvice(Advice advice) {		return (advice instanceof MethodBeforeAdvice);	}	@Override	public MethodInterceptor getInterceptor(Advisor advisor) {		MethodBeforeAdvice advice = (MethodBeforeAdvice) advisor.getAdvice();		return new MethodBeforeAdviceInterceptor(advice);	}

返回的是MethodBeforeAdviceInterceptor的对象。

目前为止，我们返回了所有相关的Interceptor的集合，我们再来看ReflectiveMethodInvocation中的proceed方法：

if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {			// Evaluate dynamic method matcher here: static part will already have			// been evaluated and found to match.			InterceptorAndDynamicMethodMatcher dm =					(InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;			if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) {				return dm.interceptor.invoke(this);			}			else {				// Dynamic matching failed.				// Skip this interceptor and invoke the next in the chain.				return proceed();			}		}		else {			// It's an interceptor, so we just invoke it: The pointcut will have			// been evaluated statically before this object was constructed.			return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);		}

 调用的便是MethodBeforeAdviceInterceptor、AfterReturningAdviceInterceptor、ThrowsAdviceInterceptor这单个Interceptor的相关的invoke方法了，分析这三个invoke方法，我们可以看见，在这里我们实现aop切面中的advice，对方法的前后实现了插入拦截。

    例如：

public class MethodBeforeAdviceInterceptor implements MethodInterceptor, Serializable {	private MethodBeforeAdvice advice;	/**	 * Create a new MethodBeforeAdviceInterceptor for the given advice.	 * @param advice the MethodBeforeAdvice to wrap	 */	public MethodBeforeAdviceInterceptor(MethodBeforeAdvice advice) {		Assert.notNull(advice, "Advice must not be null");		this.advice = advice;	}	@Override	public Object invoke(MethodInvocation mi) throws Throwable {		this.advice.before(mi.getMethod(), mi.getArguments(), mi.getThis() );		return mi.proceed();	}}

总结一下：

Spring的Aop归根到底使用的还是jdk的反射。

主要流程是这样的：

    ProxyFactoryBean(interceptorNames对象注入)——>getObject方法(初始化拦截器链)——>getSingletonInstance方法(判断target拦截对象是否为接口，使用不同的代理方式，并将ProxyFactoryBean对象注入相关代理接口)——>JdkDynamicAopProxy和ObjenesisCglibAopProxy接口调用相关的invoke方法和intercep方法作为代理的入口——>最终转化成ReflectiveMethodInvocation的proceed方法——>proceed方法中调用之前获取的拦截器链进行匹配拦截，对代理对象进行Advice切面增强。

补充拦截器链的相关过程

       ProxyFactoryBean(interceptorNames对象注入)——>getObject方法——>initializeAdvisorChain——>addAdvisorOnChainCreation()——>AdvisedSupport的addAdvisor()——>DefaultAdvisorChainFactory的getInterceptorsAndDynamicInterceptionAdvice——>DefaultAdvisorAdapterRegistry的getInterceptors进行适配并返回相关拦截器——>调用连接器链的相关拦截器进行拦截