SpringAop源码分析（基于注解）四：拦截器链

//JdkDynamicAopProxy.java

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
	MethodInvocation invocation;
	Object oldProxy = null;
	boolean setProxyContext = false;

	TargetSource targetSource = this.advised.targetSource;
	Object target = null;

	try {
		//如果目标对象没有定义equals()方法的话，就会直接调用而不会增强
<1>		if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) {
			// The target does not implement the equals(Object) method itself.
			return equals(args[0]);
		}
		//如果目标对象没有定义hashCode()方法的话，就会直接调用而不会增强
		else if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) {
			// The target does not implement the hashCode() method itself.
			return hashCode();
		}
		else if (method.getDeclaringClass() == DecoratingProxy.class) {
			// There is only getDecoratedClass() declared -> dispatch to proxy config.
			return AopProxyUtils.ultimateTargetClass(this.advised);
		}
		//Advised接口或者其父接口中定义的方法,直接反射调用,不应用通知
		else if (!this.advised.opaque && method.getDeclaringClass().isInterface() &&
				method.getDeclaringClass().isAssignableFrom(Advised.class)) {
			// Service invocations on ProxyConfig with the proxy config...
			return AopUtils.invokeJoinpointUsingReflection(this.advised, method, args);
		}

		Object retVal;

		// 如果 exposeProxy 属性为 true，则暴露代理对象
		// exposeProxy 是 @EnableAspectJAutoProxy 注解的属性之一
<2>		if (this.advised.exposeProxy) {
			// Make invocation available if necessary.
			// 向 AopContext 中设置代理对象
			oldProxy = AopContext.setCurrentProxy(proxy);
			setProxyContext = true;
		}

		//获得目标对象的类
<3>		target = targetSource.getTarget();
		Class<?> targetClass = (target != null ? target.getClass() : null);

		//获取可以应用到此方法上的 Interceptor 拦截器 列表，并且排序
<4>		List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);


		//如果没有可以应用到此方法的通知(Interceptor)，此直接反射调用 method.invoke(target, args)
<5>		if (chain.isEmpty()) {
			// We can skip creating a MethodInvocation: just invoke the target directly
			// Note that the final invoker must be an InvokerInterceptor so we know it does
			// nothing but a reflective operation on the target, and no hot swapping or fancy proxying.
			Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args);
			retVal = AopUtils.invokeJoinpointUsingReflection(target, method, argsToUse);
		}
<6>		else {
			//创建 MethodInvocation，将拦截器链放入
			invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);
			// 执行拦截器链
			retVal = invocation.proceed();
		}

		// 获取方法返回值类型
<7>		Class<?> returnType = method.getReturnType();
		if (retVal != null && retVal == target &&
				returnType != Object.class && returnType.isInstance(proxy) &&
				!RawTargetAccess.class.isAssignableFrom(method.getDeclaringClass())) {
			// 如果方法返回值为 this，即 return this; 则将代理对象 proxy 赋值给 retVal
			retVal = proxy;
		}
		// 如果返回值类型为基础类型，比如 int，long 等，当返回值为 null，抛出异常
		else if (retVal == null && returnType != Void.TYPE && returnType.isPrimitive()) {
			throw new AopInvocationException(
					"Null return value from advice does not match primitive return type for: " + method);
		}
		return retVal;
	}
	finally {
		if (target != null && !targetSource.isStatic()) {
			// Must have come from TargetSource.
			targetSource.releaseTarget(target);
		}
		if (setProxyContext) {
			// Restore old proxy.
			AopContext.setCurrentProxy(oldProxy);
		}
	}
	}

//AdvisedSupport.java

public List<Object> getInterceptorsAndDynamicInterceptionAdvice(Method method, @Nullable Class<?> targetClass) {
	MethodCacheKey cacheKey = new MethodCacheKey(method);
	//从缓存中获取
	List<Object> cached = this.methodCache.get(cacheKey);
	if (cached == null) {
		//获取所有的拦截器
		cached = this.advisorChainFactory.getInterceptorsAndDynamicInterceptionAdvice(
				this, method, targetClass);
		this.methodCache.put(cacheKey, cached);
	}
	return cached;
	}

//DefaultAdvisorChainFactory.java

/**
 * 从提供的配置实例config中获取advisor列表,遍历处理这些advisor.如果是IntroductionAdvisor,
 * 则判断此Advisor能否应用到目标类targetClass上.如果是PointcutAdvisor,则判断
 * 此Advisor能否应用到目标方法method上.将满足条件的Advisor通过AdvisorAdaptor转化成Interceptor列表返回.
 */
@Override
public List<Object> getInterceptorsAndDynamicInterceptionAdvice(
	Advised config, Method method, @Nullable Class<?> targetClass) {

    List<Object> interceptorList = new ArrayList<>(config.getAdvisors().length);
    Class<?> actualClass = (targetClass != null ? targetClass : method.getDeclaringClass());
    //查看是否包含IntroductionAdvisor
    boolean hasIntroductions = hasMatchingIntroductions(config, actualClass);
    //这里实际上注册一系列AdvisorAdapter,用于将 通知Advisor 转化成 方法拦截器MethodInterceptor
    AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();
    //遍历
    for (Advisor advisor : config.getAdvisors()) {
    	if (advisor instanceof PointcutAdvisor) {
    		PointcutAdvisor pointcutAdvisor = (PointcutAdvisor) advisor;
    		//通过ClassFilter对当前Bean类型进行匹配
    		if (config.isPreFiltered() || pointcutAdvisor.getPointcut().getClassFilter().matches(actualClass)) {
    			//将 通知Advisor 转化成 拦截器Interceptor
    			MethodInterceptor[] interceptors = registry.getInterceptors(advisor);
    			MethodMatcher mm = pointcutAdvisor.getPointcut().getMethodMatcher();
    			//检查当前advisor的pointcut是否可以匹配当前方法
    			if (MethodMatchers.matches(mm, method, actualClass, hasIntroductions)) {
    				if (mm.isRuntime()) {
    					// Creating a new object instance in the getInterceptors() method
    					// isn't a problem as we normally cache created chains.
    					for (MethodInterceptor interceptor : interceptors) {
    						//加入拦截器链
    						interceptorList.add(new InterceptorAndDynamicMethodMatcher(interceptor, mm));
    					}
    				}
    				else {
    					//加入拦截器链
    					interceptorList.addAll(Arrays.asList(interceptors));
    				}
    			}
    		}
    	}
    	else if (advisor instanceof IntroductionAdvisor) {
    		IntroductionAdvisor ia = (IntroductionAdvisor) advisor;
    		// IntroductionAdvisor 类型的通知器，仅进行类级别的匹配即可
    		if (config.isPreFiltered() || ia.getClassFilter().matches(actualClass)) {
    			Interceptor[] interceptors = registry.getInterceptors(advisor);
    			interceptorList.addAll(Arrays.asList(interceptors));
    		}
    	}
    	else {
    		Interceptor[] interceptors = registry.getInterceptors(advisor);
    		interceptorList.addAll(Arrays.asList(interceptors));
    	}
    }
    
    return interceptorList;
}

//ReflectiveMethodInvocation.java

//当前拦截器下标
private int currentInterceptorIndex = -1;
//拦截器链集合
protected final List<?> interceptorsAndDynamicMethodMatchers;

public Object proceed() throws Throwable {
	//	We start with an index of -1 and increment early.
	// 拦截器链中的最后一个拦截器执行完
	if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
		//执行目标方法
		return invokeJoinpoint();
	}

	//每次执行新的拦截器，下标+1
	Object interceptorOrInterceptionAdvice =
			this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);

	//如果要动态匹配切点
	if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {
		// Evaluate dynamic method matcher here: static part will already have
		// been evaluated and found to match.
		InterceptorAndDynamicMethodMatcher dm =
				(InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;
		// 如果是动态切点，需要进行参数匹配，以确定是否需要执行该动态横切逻辑
		if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) {
			return dm.interceptor.invoke(this);
		}
		else {
			//动态切点匹配失败,略过当前Intercetpor,调用下一个Interceptor
			return proceed();
		}
	}
	else {
		//执行当前Intercetpor
		return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
	}
	}

//AspectJAfterAdvice.java

public class AspectJAfterAdvice extends AbstractAspectJAdvice
		implements MethodInterceptor, AfterAdvice, Serializable {

	public AspectJAfterAdvice(
			Method aspectJBeforeAdviceMethod, AspectJExpressionPointcut pointcut, AspectInstanceFactory aif) {
		super(aspectJBeforeAdviceMethod, pointcut, aif);
	}


	@Override
	public Object invoke(MethodInvocation mi) throws Throwable {
		try {
			//执行下一个拦截器链
			return mi.proceed();
		}
		finally {
			//执行后置逻辑
			invokeAdviceMethod(getJoinPointMatch(), null, null);
		}
	}

	@Override
	public boolean isBeforeAdvice() {
		return false;
	}

	@Override
	public boolean isAfterAdvice() {
		return true;
	}
}

//AspectJAroundAdvice.java

public Object invoke(MethodInvocation mi) throws Throwable {
	if (!(mi instanceof ProxyMethodInvocation)) {
		throw new IllegalStateException("MethodInvocation is not a Spring ProxyMethodInvocation: " + mi);
	}
	ProxyMethodInvocation pmi = (ProxyMethodInvocation) mi;
	ProceedingJoinPoint pjp = lazyGetProceedingJoinPoint(pmi);
	JoinPointMatch jpm = getJoinPointMatch(pmi);
	//执行环绕逻辑
	return invokeAdviceMethod(pjp, jpm, null, null);
	}

@Aspect
@Component
@EnableAspectJAutoProxy
public class LogAspect {

	@Pointcut("execution(* com.mydemo.work.StudentController.getName(..))")
	private void log(){}


	@Before("log()")
	public void doBefore() {
		System.out.println("===before");
	}

	@After("execution(* com.mydemo.work.StudentController.getName(..))")
	public void doAfter() {
		System.out.println("===after");
	}

	@AfterReturning("execution(* com.mydemo.work.StudentController.getName(..))")
	public void doAfterReturn() {
		System.out.println("===afterReturn");
	}

	@Around("execution(* com.mydemo.work.StudentController.getName(..))")
	public void doAround(ProceedingJoinPoint pjp) throws Throwable {

		System.out.println("===around before");
		pjp.proceed();
		System.out.println("===around after");
	}
}

//MethodBeforeAdviceInterceptor.java

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 {
		//执行前置逻辑
		this.advice.before(mi.getMethod(), mi.getArguments(), mi.getThis() );
		//执行下一个拦截器
		return mi.proceed();
	}
}

===around before
===before
do getName
===around after
===after
===afterReturn

@Aspect
@Component
@EnableAspectJAutoProxy
@Order(2)
public class ErrorAspect {

	@Pointcut("execution(* com.mydemo.work.StudentController.getName(..))")
	private void log(){}


	@Before("log()")
	public void doBeforeError() {
		System.out.println("=== error before");
	}

	@After("execution(* com.mydemo.work.StudentController.getName(..))")
	public void doAfterError() {
		System.out.println("=== error after");
	}

	@AfterReturning("execution(* com.mydemo.work.StudentController.getName(..))")
	public void doAfterReturnError() {
		System.out.println("=== error afterReturn");
	}

	@Around("execution(* com.mydemo.work.StudentController.getName(..))")
	public void doAroundError(ProceedingJoinPoint pjp) throws Throwable {

		System.out.println("=== error around before");
		pjp.proceed();
		System.out.println("=== error around after");
	}
}

===around before
===before
=== error around before
=== error before
do getName
=== error around after
=== error after
=== error afterReturn
===around after
===after
===afterReturn

        // 如果 exposeProxy 属性为 true，则暴露代理对象
	// exposeProxy 是 @EnableAspectJAutoProxy 注解的属性之一
	if (this.advised.exposeProxy) {
		// Make invocation available if necessary.
		// 向 AopContext 中设置代理对象
		oldProxy = AopContext.setCurrentProxy(proxy);
		setProxyContext = true;
	}

public class Student implements Person {

    @Override
    public void haveFun() {
        System.out.println("篮球");
        this.hello("足球");
    }

    @Override
    public void haveFun(String action) {
        System.out.println("haveFun " +  action);
    }
}

public Object proceed() throws Throwable {
	//	We start with an index of -1 and increment early.
	// 拦截器链中的最后一个拦截器执行完
	if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
		//执行目标方法
		return invokeJoinpoint();
	}

	//...省略
		if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) {
			return dm.interceptor.invoke(this);
		}
        //...省略
	}
	else {
		//执行当前Intercetpor
		return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
	}
	}

//ReflectiveMethodInvocation.java

protected Object invokeJoinpoint() throws Throwable {
        //重点 this.target
	return AopUtils.invokeJoinpointUsingReflection(this.target, this.method, this.arguments);
	}

//ReflectiveMethodInvocation.java

public static Object invokeJoinpointUsingReflection(@Nullable Object target, Method method, Object[] args)
		throws Throwable {

	// Use reflection to invoke the method.
	try {
		ReflectionUtils.makeAccessible(method);
		//重点 target
		return method.invoke(target, args);
	}
    //...省略
	}

     // 如果 exposeProxy 属性为 true，则暴露代理对象
	// exposeProxy 是 @EnableAspectJAutoProxy 注解的属性之一
	if (this.advised.exposeProxy) {
		// Make invocation available if necessary.
		// 向 AopContext 中设置代理对象
		oldProxy = AopContext.setCurrentProxy(proxy);
		setProxyContext = true;
	}

//AopContext.java
//存储代理对象 ThreadLocal
private static final ThreadLocal<Object> currentProxy = new NamedThreadLocal<>("Current AOP proxy");

static Object setCurrentProxy(@Nullable Object proxy) {
	Object old = currentProxy.get();
	if (proxy != null) {
	        //存储代理对象到 ThreadLocal
		currentProxy.set(proxy);
	}
	else {
		currentProxy.remove();
	}
	return old;
}

public class Student implements Person {

    @Override
    @Transactional
    public void haveFun() {
        System.out.println("篮球");
        this.hello("足球");
    }

    @Override
    @Transactional
    public void haveFun(String action) {
        System.out.println("haveFun " +  action);
    }
}