【10】Spring源码-分析篇-AOP源码分析

/**
 * 切面类
 */
@Component
@EnableAspectJAutoProxy
@Aspect
public class AspectAdviceBeanUseAnnotation {

	// 定义一个全局的Pointcut
	@Pointcut("execution(* com.study.spring.sample.aop.*.do*(..))")
	public void doMethods() {
	}

	@Pointcut("execution(* com.study.spring.sample.aop.*.service*(..))")
	public void services() {
	}

	// 定义一个Before Advice
	@Before("doMethods() and args(tk,..)")
	public void before3(String tk) {
		System.out.println("----------- AspectAdviceBeanUseAnnotation before3  增强  参数tk= " + tk);
	}

	@Around("services() and args(name,..)")
	public Object around2(ProceedingJoinPoint pjp, String name) throws Throwable {
		System.out.println("--------- AspectAdviceBeanUseAnnotation arround2 参数 name=" + name);
		System.out.println("----------- AspectAdviceBeanUseAnnotation arround2 环绕-前增强 for " + pjp);
		Object ret = pjp.proceed();
		System.out.println("----------- AspectAdviceBeanUseAnnotation arround2 环绕-后增强 for " + pjp);
		return ret;
	}

	@AfterReturning(pointcut = "services()", returning = "retValue")
	public void afterReturning(Object retValue) {
		System.out.println("----------- AspectAdviceBeanUseAnnotation afterReturning 增强 , 返回值为： " + retValue);
	}

	@AfterThrowing(pointcut = "services()", throwing = "e")
	public void afterThrowing(JoinPoint jp, Exception e) {
		System.out.println("----------- AspectAdviceBeanUseAnnotation afterThrowing 增强  for " + jp);
		System.out.println("----------- AspectAdviceBeanUseAnnotation afterThrowing 增强  异常 ：" + e);
	}

	@After("doMethods()")
	public void after(JoinPoint jp) {
		System.out.println("----------- AspectAdviceBeanUseAnnotation after 增强  for " + jp);
	}

	/*
	 * BeanDefinitionRegistryPostProcessor BeanFactoryPostProcessor
	 * InstantiationAwareBeanPostProcessor Bean实例创建前后 BeanPostProcessor
	 */
}

@Component
public class BeanQ {

	public void do1(String task, int time) {
		System.out.println("-------------do1 do " + task + " time:" + time);
	}

	public String service1(String name) {
		System.out.println("-------------servce1 do " + name);
		return name;
	}

	public String service2(String name) {
		System.out.println("-------------servce2 do " + name);
		if (!"s1".equals(name)) {
			throw new IllegalArgumentException("参数 name ！= s1, name=" + name);
		}

		return name + " hello!";
	}
}

@Configuration
@ComponentScan
public class AopMainAnno {
	public static void main(String[] args) {
		ApplicationContext context = new AnnotationConfigApplicationContext(AopMainAnno.class);
		BeanQ bq = context.getBean(BeanQ.class);
		bq.do1("task1", 20);
		System.out.println();

		bq.service1("service1");

		System.out.println();
		bq.service2("s1");
	}
}

	public List<Advisor> findAdvisorBeans() {
		// Determine list of advisor bean names, if not cached already.
		String[] advisorNames = this.cachedAdvisorBeanNames;
		if (advisorNames == null) {
			// Do not initialize FactoryBeans here: We need to leave all regular beans
			// uninitialized to let the auto-proxy creator apply to them!
			// 获取当前BeanFactory中所有实现了Advisor接口的bean的名称
			advisorNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
					this.beanFactory, Advisor.class, true, false);
			this.cachedAdvisorBeanNames = advisorNames;
		}
		if (advisorNames.length == 0) {
			return new ArrayList<>();
		}

		// 对获取到的实现Advisor接口的bean的名称进行遍历
		List<Advisor> advisors = new ArrayList<>();
		// 循环所有的beanName，找出对应的增强方法
		for (String name : advisorNames) {
			// isEligibleBean()是提供的一个hook方法，用于子类对Advisor进行过滤，这里默认返回值都是true
			if (isEligibleBean(name)) {
				// 如果当前bean还在创建过程中，则略过，其创建完成之后会为其判断是否需要织入切面逻辑
				if (this.beanFactory.isCurrentlyInCreation(name)) {
					if (logger.isTraceEnabled()) {
						logger.trace("Skipping currently created advisor '" + name + "'");
					}
				}
				else {
					try {
						// 将当前bean添加到结果中
						advisors.add(this.beanFactory.getBean(name, Advisor.class));
					}
					catch (BeanCreationException ex) {
						// 对获取过程中产生的异常进行封装
						Throwable rootCause = ex.getMostSpecificCause();
						if (rootCause instanceof BeanCurrentlyInCreationException) {
							BeanCreationException bce = (BeanCreationException) rootCause;
							String bceBeanName = bce.getBeanName();
							if (bceBeanName != null && this.beanFactory.isCurrentlyInCreation(bceBeanName)) {
								if (logger.isTraceEnabled()) {
									logger.trace("Skipping advisor '" + name +
											"' with dependency on currently created bean: " + ex.getMessage());
								}
								// Ignore: indicates a reference back to the bean we're trying to advise.
								// We want to find advisors other than the currently created bean itself.
								continue;
							}
						}
						throw ex;
					}
				}
			}
		}
		return advisors;
	}

	/**
	 * 真正的创建代理，判断一些列条件，有自定义的接口的就会创建jdk代理，否则就是cglib
	 * @param config the AOP configuration in the form of an
	 * AdvisedSupport object
	 * @return
	 * @throws AopConfigException
	 */
	@Override
	public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {
		// 这段代码用来判断选择哪种创建代理对象的方式
		// config.isOptimize()   是否对代理类的生成使用策略优化 其作用是和isProxyTargetClass是一样的 默认为false
		// config.isProxyTargetClass() 是否使用Cglib的方式创建代理对象 默认为false
		// hasNoUserSuppliedProxyInterfaces目标类是否有接口存在 且只有一个接口的时候接口类型不是SpringProxy类型
		if (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) {
			// 上面的三个方法有一个为true的话，则进入到这里
			// 从AdvisedSupport中获取目标类 类对象
			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.");
			}
			// 判断目标类是否是接口 如果目标类是接口的话，则还是使用JDK的方式生成代理对象
			// 如果目标类是Proxy类型 则还是使用JDK的方式生成代理对象
			if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) {
				return new JdkDynamicAopProxy(config);
			}
			// 配置了使用Cglib进行动态代理或者目标类没有接口,那么使用Cglib的方式创建代理对象
			return new ObjenesisCglibAopProxy(config);
		}
		else {
			// 使用JDK的提供的代理方式生成代理对象
			return new JdkDynamicAopProxy(config);
		}
	}

public class ProxyConfig implements Serializable {

	/** use serialVersionUID from Spring 1.2 for interoperability. */
	private static final long serialVersionUID = -8409359707199703185L;

	// 是否代理的对象是类，动态代理分为代理接口和类，这里的属性默认是代理的接口
	private boolean proxyTargetClass = false;
	// 是否进行主动优化，默认是不会主动优化
	private boolean optimize = false;
	// 是否由此配置创建的代理不能被转成Advised类型，默认时候可转
	boolean opaque = false;
	// 是否会暴露代理在调用的时候，默认是不会暴露
	boolean exposeProxy = false;
	// 是否冻结此配置，不能被修改
	private boolean frozen = false;

}

	@Override
	protected boolean shouldSkip(Class<?> beanClass, String beanName) {
		// TODO: Consider optimization by caching the list of the aspect names
		List<Advisor> candidateAdvisors = findCandidateAdvisors();
		for (Advisor advisor : candidateAdvisors) {
			if (advisor instanceof AspectJPointcutAdvisor &&
					((AspectJPointcutAdvisor) advisor).getAspectName().equals(beanName)) {
				return true;
			}
		}
		return super.shouldSkip(beanClass, beanName);
	}

	/**
	 * 查找通知器
	 * @return
	 */
	@Override
	protected List<Advisor> findCandidateAdvisors() {
		// Add all the Spring advisors found according to superclass rules.
		// 找到系统中实现了Advisor接口的bean
		List<Advisor> advisors = super.findCandidateAdvisors();
		// Build Advisors for all AspectJ aspects in the bean factory.
		if (this.aspectJAdvisorsBuilder != null) {
			// 找到系统中使用@Aspect标注的bean，并且找到该bean中使用@Before，@After等标注的方法，
			// 将这些方法封装为一个个Advisor
			advisors.addAll(this.aspectJAdvisorsBuilder.buildAspectJAdvisors());
		}
		return advisors;
	}

	public List<Advisor> buildAspectJAdvisors() {
		// 获取切面名字列表
		List<String> aspectNames = this.aspectBeanNames;

		// 缓存字段aspectNames没有值,注意实例化第一个单实例bean的时候就会触发解析切面
		if (aspectNames == null) {
			// 双重检查
			synchronized (this) {
				aspectNames = this.aspectBeanNames;
				if (aspectNames == null) {
					// 用于保存所有解析出来的Advisors集合对象
					List<Advisor> advisors = new ArrayList<>();
					// 用于保存切面的名称的集合
					aspectNames = new ArrayList<>();
					/**
					 * AOP功能中在这里传入的是Object对象，代表去容器中获取到所有的组件的名称，然后再
					 * 进行遍历，这个过程是十分的消耗性能的，所以说Spring会再这里加入了保存切面信息的缓存。
					 * 但是事务功能不一样，事务模块的功能是直接去容器中获取Advisor类型的，选择范围小，且不消耗性能。
					 * 所以Spring在事务模块中没有加入缓存来保存我们的事务相关的advisor
					 */
					String[] beanNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
							this.beanFactory, Object.class, true, false);
					// 遍历我们从IOC容器中获取处的所有Bean的名称
					for (String beanName : beanNames) {
						// 判断当前bean是否为子类定制的需要过滤的bean
						if (!isEligibleBean(beanName)) {
							continue;
						}
						// We must be careful not to instantiate beans eagerly as in this case they
						// would be cached by the Spring container but would not have been weaved.
						// 通过beanName去容器中获取到对应class对象
						Class<?> beanType = this.beanFactory.getType(beanName, false);
						if (beanType == null) {
							continue;
						}
						// 判断当前bean是否使用了@Aspect注解进行标注
						if (this.advisorFactory.isAspect(beanType)) {
							aspectNames.add(beanName);
							// 对于使用了@Aspect注解标注的bean，将其封装为一个AspectMetadata类型。
							// 这里在封装的过程中会解析@Aspect注解上的参数指定的切面类型，如perthis
							// 和pertarget等。这些被解析的注解都会被封装到其perClausePointcut属性中
							AspectMetadata amd = new AspectMetadata(beanType, beanName);
							// 判断@Aspect注解中标注的是否为singleton类型，默认的切面类都是singleton类型
							if (amd.getAjType().getPerClause().getKind() == PerClauseKind.SINGLETON) {
								// 将BeanFactory和当前bean封装为MetadataAwareAspect-
								// InstanceFactory对象，这里会再次将@Aspect注解中的参数都封装
								// 为一个AspectMetadata，并且保存在该factory中
								MetadataAwareAspectInstanceFactory factory =
										new BeanFactoryAspectInstanceFactory(this.beanFactory, beanName);
								// 通过封装的bean获取其Advice，如@Before，@After等等，并且将这些
								// Advice都解析并且封装为一个个的Advisor
								List<Advisor> classAdvisors = this.advisorFactory.getAdvisors(factory);
								// 如果切面类是singleton类型，则将解析得到的Advisor进行缓存，
								// 否则将当前的factory进行缓存，以便再次获取时可以通过factory直接获取
								if (this.beanFactory.isSingleton(beanName)) {
									this.advisorsCache.put(beanName, classAdvisors);
								}
								else {
									this.aspectFactoryCache.put(beanName, factory);
								}
								advisors.addAll(classAdvisors);
							}
							else {
								// Per target or per this.
								// 如果@Aspect注解标注的是perthis和pertarget类型，说明当前切面
								// 不可能是单例的，因而这里判断其如果是单例的则抛出异常
								if (this.beanFactory.isSingleton(beanName)) {
									throw new IllegalArgumentException("Bean with name '" + beanName +
											"' is a singleton, but aspect instantiation model is not singleton");
								}
								// 将当前BeanFactory和切面bean封装为一个多例类型的Factory
								MetadataAwareAspectInstanceFactory factory =
										new PrototypeAspectInstanceFactory(this.beanFactory, beanName);
								// 对当前bean和factory进行缓存
								this.aspectFactoryCache.put(beanName, factory);
								advisors.addAll(this.advisorFactory.getAdvisors(factory));
							}
						}
					}
					this.aspectBeanNames = aspectNames;
					return advisors;
				}
			}
		}

		if (aspectNames.isEmpty()) {
			return Collections.emptyList();
		}
		// 通过所有的aspectNames在缓存中获取切面对应的Advisor，这里如果是单例的，则直接从advisorsCache
		// 获取，如果是多例类型的，则通过MetadataAwareAspectInstanceFactory立即生成一个
		List<Advisor> advisors = new ArrayList<>();
		for (String aspectName : aspectNames) {
			List<Advisor> cachedAdvisors = this.advisorsCache.get(aspectName);
			// 如果是单例的Advisor bean，则直接添加到返回值列表中
			if (cachedAdvisors != null) {
				advisors.addAll(cachedAdvisors);
			}
			else {
				// 如果是多例的Advisor bean，则通过MetadataAwareAspectInstanceFactory生成
				MetadataAwareAspectInstanceFactory factory = this.aspectFactoryCache.get(aspectName);
				advisors.addAll(this.advisorFactory.getAdvisors(factory));
			}
		}
		return advisors;
	}

	@Override
	public List<Advisor> getAdvisors(MetadataAwareAspectInstanceFactory aspectInstanceFactory) {
		// 获取标记为AspectJ的类
		Class<?> aspectClass = aspectInstanceFactory.getAspectMetadata().getAspectClass();
		// 获取标记为AspectJ的name
		String aspectName = aspectInstanceFactory.getAspectMetadata().getAspectName();
		// 对当前切面bean进行校验，主要是判断其切点是否为perflow或者是percflowbelow，Spring暂时不支持
		// 这两种类型的切点
		validate(aspectClass);

		// We need to wrap the MetadataAwareAspectInstanceFactory with a decorator
		// so that it will only instantiate once.
		// 将当前aspectInstanceFactory进行封装，这里LazySingletonAspectInstanceFactoryDecorator
		// 使用装饰器模式，主要是对获取到的切面实例进行了缓存，保证每次获取到的都是同一个切面实例
		MetadataAwareAspectInstanceFactory lazySingletonAspectInstanceFactory =
				new LazySingletonAspectInstanceFactoryDecorator(aspectInstanceFactory);

		List<Advisor> advisors = new ArrayList<>();
		// 这里getAdvisorMethods()会获取所有的没有使用@Pointcut注解标注的方法，然后对其进行遍历
		for (Method method : getAdvisorMethods(aspectClass)) {
			// Prior to Spring Framework 5.2.7, advisors.size() was supplied as the declarationOrderInAspect
			// to getAdvisor(...) to represent the "current position" in the declared methods list.
			// However, since Java 7 the "current position" is not valid since the JDK no longer
			// returns declared methods in the order in which they are declared in the source code.
			// Thus, we now hard code the declarationOrderInAspect to 0 for all advice methods
			// discovered via reflection in order to support reliable advice ordering across JVM launches.
			// Specifically, a value of 0 aligns with the default value used in
			// AspectJPrecedenceComparator.getAspectDeclarationOrder(Advisor).
			// 判断当前方法是否标注有@Before，@After或@Around等注解，如果标注了，则将其封装为一个Advisor
			Advisor advisor = getAdvisor(method, lazySingletonAspectInstanceFactory, 0, aspectName);
			if (advisor != null) {
				advisors.add(advisor);
			}
		}

		// If it's a per target aspect, emit the dummy instantiating aspect.
		// 这里的isLazilyInstantiated()方法判断的是当前bean是否应该被延迟初始化，其主要是判断当前
		// 切面类是否为perthis，pertarget或pertypewithiin等声明的切面。因为这些类型所环绕的目标bean
		// 都是多例的，因而需要在运行时动态判断目标bean是否需要环绕当前的切面逻辑
		if (!advisors.isEmpty() && lazySingletonAspectInstanceFactory.getAspectMetadata().isLazilyInstantiated()) {
			// 如果Advisor不为空，并且是需要延迟初始化的bean，则在第0位位置添加一个同步增强器，
			// 该同步增强器实际上就是一个BeforeAspect的Advisor
			Advisor instantiationAdvisor = new SyntheticInstantiationAdvisor(lazySingletonAspectInstanceFactory);
			advisors.add(0, instantiationAdvisor);
		}

		// Find introduction fields.
		// 判断属性上是否包含有@DeclareParents注解标注的需要新添加的属性，如果有，则将其封装为一个Advisor
		for (Field field : aspectClass.getDeclaredFields()) {
			Advisor advisor = getDeclareParentsAdvisor(field);
			if (advisor != null) {
				advisors.add(advisor);
			}
		}

		return advisors;
	}

	@Nullable
	public Advisor getAdvisor(Method candidateAdviceMethod, MetadataAwareAspectInstanceFactory aspectInstanceFactory,
			int declarationOrderInAspect, String aspectName) {
		// 校验当前切面类是否使用了perflow或者percflowbelow标识的切点，Spring暂不支持这两种切点
		validate(aspectInstanceFactory.getAspectMetadata().getAspectClass());

		// 获取当前方法中@Before，@After或者@Around等标注的注解，并且获取该注解的值，将其
		// 封装为一个AspectJExpressionPointcut对象
		AspectJExpressionPointcut expressionPointcut = getPointcut(
				candidateAdviceMethod, aspectInstanceFactory.getAspectMetadata().getAspectClass());
		if (expressionPointcut == null) {
			return null;
		}

		// 将获取到的切点，切点方法等信息封装为一个Advisor对象，也就是说当前Advisor包含有所有
		// 当前切面进行环绕所需要的信息
		return new InstantiationModelAwarePointcutAdvisorImpl(expressionPointcut, candidateAdviceMethod,
				this, aspectInstanceFactory, declarationOrderInAspect, aspectName);
	}

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

		// 获取到我们的目标对象
		TargetSource targetSource = this.advised.targetSource;
		Object target = null;

		try {
			// 若是equals方法不需要代理
			if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) {
				// The target does not implement the equals(Object) method itself.
				return equals(args[0]);
			}
			// 若是hashCode方法不需要代理
			else if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) {
				// The target does not implement the hashCode() method itself.
				return hashCode();
			}
			// 若是DecoratingProxy也不要拦截器执行
			else if (method.getDeclaringClass() == DecoratingProxy.class) {
				// There is only getDecoratedClass() declared -> dispatch to proxy config.
				return AopProxyUtils.ultimateTargetClass(this.advised);
			}
			// isAssignableFrom方法：如果调用这个方法的class或接口与参数cls表示的类或接口相同，或者是参数cls表示的类或接口的父类，则返回true
			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;

			/**
			 * 这个配置是暴露我们的代理对象到线程变量中，需要搭配@EnableAspectJAutoProxy(exposeProxy = true)一起使用
			 * 比如在目标对象方法中再次获取代理对象可以使用这个AopContext.currentProxy()
			 * 还有的就是事务方法调用事务方法的时候也是用到这个
			 */
			if (this.advised.exposeProxy) {
				// Make invocation available if necessary.
				// 把我们的代理对象暴露到线程变量中
				oldProxy = AopContext.setCurrentProxy(proxy);
				setProxyContext = true;
			}

			// Get as late as possible to minimize the time we "own" the target,
			// in case it comes from a pool.
			// 获取我们的目标对象
			target = targetSource.getTarget();
			// 获取我们目标对象的class
			Class<?> targetClass = (target != null ? target.getClass() : null);

			// Get the interception chain for this method.
			// 从Advised中根据方法名和目标类获取AOP拦截器执行链
			List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);

			// Check whether we have any advice. If we don't, we can fallback on direct
			// reflective invocation of the target, and avoid creating a MethodInvocation.
			// 如果拦截器链为空
			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.
				// 通过反射直接调用执行
				Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args);
				// 如果没有发现任何拦截器那么直接调用切点方法
				retVal = AopUtils.invokeJoinpointUsingReflection(target, method, argsToUse);
			}
			else {
				// We need to create a method invocation...
				// 将拦截器封装在ReflectiveMethodInvocation，以便于使用其proceed进行处理
				MethodInvocation invocation =
						new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);
				// Proceed to the joinpoint through the interceptor chain.
				// 执行拦截器链
				retVal = invocation.proceed();
			}

			// Massage return value if necessary.
			// 获取返回类型
			Class<?> returnType = method.getReturnType();
			if (retVal != null && retVal == target &&
					returnType != Object.class && returnType.isInstance(proxy) &&
					!RawTargetAccess.class.isAssignableFrom(method.getDeclaringClass())) {
				// Special case: it returned "this" and the return type of the method
				// is type-compatible. Note that we can't help if the target sets
				// a reference to itself in another returned object.
				retVal = proxy;
			}
			// 返回值类型错误
			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 {
			// 如果目标对象不为空且目标对象是可变的,如prototype类型
			// 通常我们的目标对象都是单例的,即targetSource.isStatic为true
			if (target != null && !targetSource.isStatic()) {
				// Must have come from TargetSource.
				// 释放目标对象
				targetSource.releaseTarget(target);
			}
			if (setProxyContext) {
				// Restore old proxy.
				// 线程上下文复位
				AopContext.setCurrentProxy(oldProxy);
			}
		}
	}

	/**
	 * 递归获取通知，然后执行
	 * @return
	 * @throws Throwable
	 */
	@Override
	@Nullable
	public Object proceed() throws Throwable {
		// We start with an index of -1 and increment early.
		// 从索引为-1的拦截器开始调用，并按序递增，如果拦截器链中的拦截器迭代调用完毕，开始调用target的函数，这个函数是通过反射机制完成的
		// 具体实现在AopUtils.invokeJoinpointUsingReflection方法中
		if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
			return invokeJoinpoint();
		}

		// 获取下一个要执行的拦截器，沿着定义好的interceptorOrInterceptionAdvice链进行处理
		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.
			// 这里对拦截器进行动态匹配的判断，这里是对pointcut触发进行匹配的地方，如果和定义的pointcut匹配，那么这个advice将会得到执行
			InterceptorAndDynamicMethodMatcher dm =
					(InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;
			Class<?> targetClass = (this.targetClass != null ? this.targetClass : this.method.getDeclaringClass());
			if (dm.methodMatcher.matches(this.method, targetClass, this.arguments)) {
				return dm.interceptor.invoke(this);
			}
			else {
				// Dynamic matching failed.
				// Skip this interceptor and invoke the next in the chain.
				// 如果不匹配，那么proceed会被递归调用，知道所有的拦截器都被运行过位置
				return proceed();
			}
		}
		else {
			// It's an interceptor, so we just invoke it: The pointcut will have
			// been evaluated statically before this object was constructed.
			// 普通拦截器，直接调用拦截器，将this作为参数传递以保证当前实例中调用链的执行
			return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
		}
	}