Spring学习系列之AOP实现机制分析

public class TestFileSystemXmlApplicationContext {
//     xml文件中声明方式实现AOP
    public static void main(String[] args) {
        FileSystemXmlApplicationContext context = new FileSystemXmlApplicationContext("beans.xml");
        Wait waiter = (Wait) context.getBean("waiter");
        waiter.say();
        context.close();
    }

    // 编程方式实现AOP
//    private static SayHelloBeforemale male ;
//    private static Waiter wait;
//    private static ProxyFactory xy;
//
//    public static void main(String[] args) {
//        //实例化并赋值
//        male = new SayHelloBeforemale();
//        wait = new Waiter();
//        xy = new ProxyFactory();
//        //设置目标对象
//        xy.setTarget(wait);
//        //设置增强类对象
//        xy.addAdvice(male);
//
//        Waiter w = (Waiter)xy.getProxy();
//        w.say();
//    }
}

public interface Wait {
    void say();
}

public class Waiter implements Wait {
    @Override
    public void say() {
        // TODO Auto-generated method stub
        System.out.println("先生");
    }
}

public class SayHelloBeforemale implements MethodBeforeAdvice {
    @Override
    public void before(Method method, Object[] args, Object target) throws Throwable {
        System.out.println("hello");
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd">    

    <!--定义advise sayhelloadvice定义了通知包含什么-->
    <bean id="sayhelloadvice" class="mytests.aopTests.SayHelloBeforemale"/>

    <!--waiter定义了在何时(调用proxyInterfaces接口的方法时)为什么对象(target指定，此对象需要实现proxyInterfaces接口)-->
    <!--应用何种通知(interceptorNames中指定)-->
    <!-- 定义advisor-->
    <bean id="waiter" class="org.springframework.aop.framework.ProxyFactoryBean">        
        <property name="target">
            <bean class="mytests.aopTests.Waiter"/>
        </property>
        <property name="interceptorNames">
            <list>
                <value>sayhelloadvice</value>
            </list>
        </property>
    </bean>
</beans>

public class ProxyFactoryBean extends ProxyCreatorSupport
		implements FactoryBean<Object>, BeanClassLoaderAware, BeanFactoryAware {

    /**
	 * Return a proxy. Invoked when clients obtain beans from this factory bean.
	 * Create an instance of the AOP proxy to be returned by this factory.
	 * The instance will be cached for a singleton, and create on each call to
	 * {@code getObject()} for a proxy.
	 * @return a fresh AOP proxy reflecting the current state of this factory
	 * 
	 */
	public Object getObject() throws BeansException {
        // 如果尚未初始化过通知器链则进行初始化
		initializeAdvisorChain();
        // 这里对singleton和prototype的类型进行区分，生成对应的proxy
		if (isSingleton()) {
			return getSingletonInstance();
		}
		else {
			if (this.targetName == null) {
				logger.warn("Using non-singleton proxies with singleton targets is often undesirable. " +
						"Enable prototype proxies by setting the 'targetName' property.");
			}
			return newPrototypeInstance();
		}
	}

    /**
	 * Create the advisor (interceptor) chain. Advisors that are sourced
	 * from a BeanFactory will be refreshed each time a new prototype instance
	 * is added. Interceptors added programmatically through the factory API
	 * are unaffected by such changes.
	 */
	private synchronized void initializeAdvisorChain() throws AopConfigException, BeansException {
		if (this.advisorChainInitialized) {
			return;
		}

		if (!ObjectUtils.isEmpty(this.interceptorNames)) {
			if (this.beanFactory == null) {
				throw new IllegalStateException("No BeanFactory available anymore (probably due to serialization) " +
						"- cannot resolve interceptor names " + Arrays.asList(this.interceptorNames));
			}

			// Globals can't be last unless we specified a targetSource using the property...
			if (this.interceptorNames[this.interceptorNames.length - 1].endsWith(GLOBAL_SUFFIX) &&
					this.targetName == null && this.targetSource == EMPTY_TARGET_SOURCE) {
				throw new AopConfigException("Target required after globals");
			}

			// Materialize interceptor chain from bean names.
            // 添加Advisor链的调用，是通过beans.xml中interceptorNames属性来配置的
			for (String name : this.interceptorNames) {
				if (logger.isTraceEnabled()) {
					logger.trace("Configuring advisor or advice '" + name + "'");
				}
                // 全局Advisor
				if (name.endsWith(GLOBAL_SUFFIX)) {
					if (!(this.beanFactory instanceof ListableBeanFactory)) {
						throw new AopConfigException(
								"Can only use global advisors or interceptors with a ListableBeanFactory");
					}
					addGlobalAdvisor((ListableBeanFactory) this.beanFactory,
							name.substring(0, name.length() - GLOBAL_SUFFIX.length()));
				}
                // beans.xml中手动配置的Advisor
				else {
					// If we get here, we need to add a named interceptor.
					// We must check if it's a singleton or prototype.
                    /**
                     * 程序执行到这里说明需要加入指定名称的拦截器Advice，并且需要检查这个bean是singleton还是
                     * prototype类型
                     */
					Object advice;
					if (this.singleton || this.beanFactory.isSingleton(name)) {
						// Add the real Advisor/Advice to the chain.
						advice = this.beanFactory.getBean(name);
					}
					else {
						// It's a prototype Advice or Advisor: replace with a prototype.
						// Avoid unnecessary creation of prototype bean just for advisor chain initialization.
						advice = new PrototypePlaceholderAdvisor(name);
					}
					addAdvisorOnChainCreation(advice, name);
				}
			}
		}
        // 初始化完成标志
		this.advisorChainInitialized = true;
	}

    /**
	 * Add all global interceptors and pointcuts.
	 * 在所有的global interceptors and pointcut中筛选出名字符合传入的prefix的，加入到通知器链中
	 */
	private void addGlobalAdvisor(ListableBeanFactory beanFactory, String prefix) {
		String[] globalAdvisorNames =
				BeanFactoryUtils.beanNamesForTypeIncludingAncestors(beanFactory, Advisor.class);
		String[] globalInterceptorNames =
				BeanFactoryUtils.beanNamesForTypeIncludingAncestors(beanFactory, Interceptor.class);
		List<Object> beans = new ArrayList<Object>(globalAdvisorNames.length + globalInterceptorNames.length);
		Map<Object, String> names = new HashMap<Object, String>(beans.size());
		for (String name : globalAdvisorNames) {
			Object bean = beanFactory.getBean(name);
			beans.add(bean);
			names.put(bean, name);
		}
		for (String name : globalInterceptorNames) {
			Object bean = beanFactory.getBean(name);
			beans.add(bean);
			names.put(bean, name);
		}
		OrderComparator.sort(beans);
		for (Object bean : beans) {
			String name = names.get(bean);
			if (name.startsWith(prefix)) {
				addAdvisorOnChainCreation(bean, name);
			}
		}
	}

    /**
	 * Invoked when advice chain is created.
	 * <p>Add the given advice, advisor or object to the interceptor list.
	 * Because of these three possibilities, we can't type the signature
	 * more strongly.
	 * @param next advice, advisor or target object
	 * @param name bean name from which we obtained this object in our owning
	 * bean factory
	 * next：要加入到通知器链中的Advice
	 * name：beans.xml中为Advice设置的名称
	 */
	private void addAdvisorOnChainCreation(Object next, String name) {
		// We need to convert to an Advisor if necessary so that our source reference
		// matches what we find from superclass interceptors.
        // 将一个advice对象通过适配器适配为advisor对象
		Advisor advisor = namedBeanToAdvisor(next);
		if (logger.isTraceEnabled()) {
			logger.trace("Adding advisor with name '" + name + "'");
		}
        // 调用AdvisedSupport.addAdvisor
		addAdvisor(advisor);
	}
    
    /**
	 * Convert the following object sourced from calling getBean() on a name in the
	 * interceptorNames array to an Advisor or TargetSource.
	 */
	private Advisor namedBeanToAdvisor(Object next) {
		try {
            // 调用DefaultAdvisorAdapterRegistry.wrap方法将interceptorNames对应的Advice封装为一个Advisor
			return this.advisorAdapterRegistry.wrap(next);
		}
		catch (UnknownAdviceTypeException ex) {
			// We expected this to be an Advisor or Advice,
			// but it wasn't. This is a configuration error.
			throw new AopConfigException("Unknown advisor type " + next.getClass() +
					"; Can only include Advisor or Advice type beans in interceptorNames chain except for last entry," +
					"which may also be target or TargetSource", ex);
		}
	}       
}

public class AdvisedSupport extends ProxyConfig implements Advised {

    /**
	 * List of Advisors. If an Advice is added, it will be wrapped
	 * in an Advisor before being added to this List.
	 * 保存ProxyFactoryBean中的Advisors
	 */
	private List<Advisor> advisors = new LinkedList<Advisor>();

    public void addAdvisor(Advisor advisor) {
		int pos = this.advisors.size();
		addAdvisor(pos, advisor);
	}

    public void addAdvisor(int pos, Advisor advisor) throws AopConfigException {
		if (advisor instanceof IntroductionAdvisor) {
			validateIntroductionAdvisor((IntroductionAdvisor) advisor);
		}
		addAdvisorInternal(pos, advisor);
	}
   
    // 真正的addAdvisor方法
    private void addAdvisorInternal(int pos, Advisor advisor) throws AopConfigException {
		Assert.notNull(advisor, "Advisor must not be null");
		if (isFrozen()) {
			throw new AopConfigException("Cannot add advisor: Configuration is frozen.");
		}
		if (pos > this.advisors.size()) {
			throw new IllegalArgumentException(
					"Illegal position " + pos + " in advisor list with size " + this.advisors.size());
		}
		this.advisors.add(pos, advisor);
		updateAdvisorArray();
		adviceChanged();
	}
}

public class ProxyFactoryBean extends ProxyCreatorSupport
		implements FactoryBean<Object>, BeanClassLoaderAware, BeanFactoryAware {

    /**
	 * Return a proxy. Invoked when clients obtain beans from this factory bean.
	 * Create an instance of the AOP proxy to be returned by this factory.
	 * The instance will be cached for a singleton, and create on each call to
	 * {@code getObject()} for a proxy.
	 * @return a fresh AOP proxy reflecting the current state of this factory
	 * 
	 */
	public Object getObject() throws BeansException {
        // 如果尚未初始化过通知器链则进行初始化
		initializeAdvisorChain();
        // 这里对singleton和prototype的类型进行区分，生成对应的proxy
		if (isSingleton()) {
			return getSingletonInstance();
		}
		else {
			if (this.targetName == null) {
				logger.warn("Using non-singleton proxies with singleton targets is often undesirable. " +
						"Enable prototype proxies by setting the 'targetName' property.");
			}
			return newPrototypeInstance();
		}
	}

    /**
	 * Return the singleton instance of this class's proxy object,
	 * lazily creating it if it hasn't been created already.
	 * @return the shared singleton proxy
	 */
	private synchronized Object getSingletonInstance() {
		if (this.singletonInstance == null) {
			this.targetSource = freshTargetSource();
			if (this.autodetectInterfaces && getProxiedInterfaces().length == 0 && !isProxyTargetClass()) {
				// Rely on AOP infrastructure to tell us what interfaces to proxy.
                // 根据AOP框架来判断需要代理的接口
				Class<?> targetClass = getTargetClass();
				if (targetClass == null) {
					throw new FactoryBeanNotInitializedException("Cannot determine target class for proxy");
				}
                // 设置代理对象要实现的接口
				setInterfaces(ClassUtils.getAllInterfacesForClass(targetClass, this.proxyClassLoader));
			}
			// Initialize the shared singleton instance.
			super.setFrozen(this.freezeProxy);
            // 注意这里的方法会使用ProxyFactory来生成需要的Proxy
            // 每次调用都会创建一个新的AopProxy类对象
			this.singletonInstance = getProxy(createAopProxy());
		}
		return this.singletonInstance;
	}
    
    // 通过createAopProxy返回的AopProxy来生成代理对象
    // 这里传入的AopProxy类对象可能是一个JdkDynamicAopProxy类的对象，其内部持有ProxyFactoryBean的引用
    // 每个JdkDynamicAopProxy每次调用getProxy获取的Proxy对象都是新的
    protected Object getProxy(AopProxy aopProxy) {
		return aopProxy.getProxy(this.proxyClassLoader);
	}
}

public class ProxyCreatorSupport extends AdvisedSupport {

    /**
	 * Subclasses should call this to get a new AOP proxy. They should <b>not</b>
	 * create an AOP proxy with {@code this} as an argument.
	 */
	protected final synchronized AopProxy createAopProxy() {
		if (!this.active) {
			activate();
		}
		return getAopProxyFactory().createAopProxy(this);
	}

    /**
	 * Return the AopProxyFactory that this ProxyConfig uses.
	 */
	public AopProxyFactory getAopProxyFactory() {
		return this.aopProxyFactory;
	}

    /**
	 * Create a new ProxyCreatorSupport instance.
	 * 默认的aopProxyFactory
	 */
	public ProxyCreatorSupport() {
		this.aopProxyFactory = new DefaultAopProxyFactory();
	}
}

public class DefaultAopProxyFactory implements AopProxyFactory, Serializable {

    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.");
			}
            // 如果targetClass是接口类，使用JDK动态代理
			if (targetClass.isInterface()) {
				return new JdkDynamicAopProxy(config);
			}
            // 非接口类使用CGLIB动态代理
			return CglibProxyFactory.createCglibProxy(config);
		}
		else {
			return new JdkDynamicAopProxy(config);
		}
	}
}

final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable {

    /** 
     * Config used to configure this proxy
     * 可能是一个 ProxyFactoryBean 类的实例
     */
	private final AdvisedSupport advised;

    public JdkDynamicAopProxy(AdvisedSupport config) throws AopConfigException {
		Assert.notNull(config, "AdvisedSupport must not be null");
		if (config.getAdvisors().length == 0 && config.getTargetSource() == AdvisedSupport.EMPTY_TARGET_SOURCE) {
			throw new AopConfigException("No advisors and no TargetSource specified");
		}
		this.advised = config;
	}

    public Object getProxy(ClassLoader classLoader) {
		if (logger.isDebugEnabled()) {
			logger.debug("Creating JDK dynamic proxy: target source is " + this.advised.getTargetSource());
		}
		Class<?>[] proxiedInterfaces = AopProxyUtils.completeProxiedInterfaces(this.advised);
		findDefinedEqualsAndHashCodeMethods(proxiedInterfaces);
		return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this);
	}
    
}

final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable {

    /** 
     * Config used to configure this proxy
     * 可能是一个 ProxyFactoryBean 类的实例
     */
	private final AdvisedSupport advised;

    /**
	 * Implementation of {@code InvocationHandler.invoke}.
	 * <p>Callers will see exactly the exception thrown by the target,
	 * unless a hook method throws an exception.
	 * 动态代理生成的类会调用这个类的invoke方法对实际对象的方法进行拦截，之后再调用实际对象的方法 
	 */
	public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
		MethodInvocation invocation;
		Object oldProxy = null;
		boolean setProxyContext = false;

		TargetSource targetSource = this.advised.targetSource;
		Class<?> targetClass = null;
		Object target = null;

		try {
			if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) {
				// The target does not implement the equals(Object) method itself.
                // 如果目标对象没有实现Object类的基本方法equals
				return equals(args[0]);
			}
			if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) {
				// The target does not implement the hashCode() method itself.
                // 如果目标对象没有实现Object类的基本方法hashCode
				return hashCode();
			}
			if (!this.advised.opaque && method.getDeclaringClass().isInterface() &&
					method.getDeclaringClass().isAssignableFrom(Advised.class)) {
				// Service invocations on ProxyConfig with the proxy config...
                // 根据代理对象的配置来调用服务 何时会出现这种情况？？？  
				return AopUtils.invokeJoinpointUsingReflection(this.advised, method, args);
			}

			Object retVal;

			if (this.advised.exposeProxy) {
				// Make invocation available if necessary.
				oldProxy = AopContext.setCurrentProxy(proxy);
				setProxyContext = true;
			}

			// May be null. Get as late as possible to minimize the time we "own" the target,
			// in case it comes from a pool.
            // 获取被代理的目标对象
			target = targetSource.getTarget();
			if (target != null) {
				targetClass = target.getClass();
			}

			// Get the interception chain for this method.
            // 获得定义好的拦截器链
			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.
            // 如果没有设定拦截器，那么就直接调用target的对应方法
			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.
				retVal = AopUtils.invokeJoinpointUsingReflection(target, method, args);
			}
			else {
				// We need to create a method invocation...
                // 如果有拦截器的设定，那么需要调用拦截器之后才调用目标对象的相应方法
                // 通过构造一个ReflectiveMethodInvocation来实现，下面会介绍
                // 这个ReflectiveMethodInvocation类的具体实现
				invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);
				
                // Proceed to the joinpoint through the interceptor chain.
                // 沿着拦截器链继续前进
				retVal = invocation.proceed();
			}

			// Massage return value if necessary.
			Class<?> returnType = method.getReturnType();
			if (retVal != null && retVal == target && 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;
			}
			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);
			}
		}
	}
    
}

public class ReflectiveMethodInvocation implements ProxyMethodInvocation, Cloneable {

    protected final Object proxy;

	protected final Object target;

	protected final Method method;

	protected Object[] arguments;

	private final Class targetClass;

    /**
	 * Lazily initialized map of user-specific attributes for this invocation.
	 */
	private Map<String, Object> userAttributes;

    /**
	 * List of MethodInterceptor and InterceptorAndDynamicMethodMatcher
	 * that need dynamic checks.
	 */
	protected final List interceptorsAndDynamicMethodMatchers;

    protected ReflectiveMethodInvocation(
			Object proxy, Object target, Method method, Object[] arguments,
			Class targetClass, List<Object> interceptorsAndDynamicMethodMatchers) {

		this.proxy = proxy;
		this.target = target;
		this.targetClass = targetClass;
		this.method = BridgeMethodResolver.findBridgedMethod(method);
		this.arguments = arguments;
		this.interceptorsAndDynamicMethodMatchers = interceptorsAndDynamicMethodMatchers;
	}

    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成，这里开始调用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中
		if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
			return invokeJoinpoint();
		}

        // 这里沿着定义好的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，这里就是触发对前面分析的pointCut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;
			if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) {
                // this引用的传入使得在interceptor.invoke方法中可以继续调用proceed方法
				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，直到所有的拦截器都被运行过为止
				return proceed();
			}
		}
		else {
			// It's an interceptor, so we just invoke it: The pointcut will have
			// been evaluated statically before this object was constructed.
            // 如果是一个interceptor，直接调用这个interceptor对应的方法就好
			return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
		}
	}
    
    // target是被代理的实际对象，这里调用的实际对象的方法，在拦截器执行完成之后调用
    protected Object invokeJoinpoint() throws Throwable {
		return AopUtils.invokeJoinpointUsingReflection(this.target, this.method, this.arguments);
	}
}

// 获得定义好的拦截器链
List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);

public class AdvisedSupport extends ProxyConfig implements Advised {

    /**
	 * Determine a list of {@link org.aopalliance.intercept.MethodInterceptor} objects
	 * for the given method, based on this configuration.
	 * 在当前ProxyFactoryBean中获取被代理对象指定方法名称的拦截器链
	 * @param method the proxied method
	 * @param targetClass the target class
	 * @return List of MethodInterceptors (may also include InterceptorAndDynamicMethodMatchers)
	 */
	public List<Object> getInterceptorsAndDynamicInterceptionAdvice(Method method, Class targetClass) {
		MethodCacheKey cacheKey = new MethodCacheKey(method);
        // 先从缓存中找
		List<Object> cached = this.methodCache.get(cacheKey);
        // 没有找到
		if (cached == null) {
            // 根据method参数获取与其对应的拦截器链的工作是由advisorChainFactory来完成的
            // 这里使用的是DefaultAdvisorChainFactory
            // 这里的this可以是一个ProxyFactoryBean类的实现
			cached = this.advisorChainFactory.getInterceptorsAndDynamicInterceptionAdvice(
					this, method, targetClass);
			this.methodCache.put(cacheKey, cached);
		}
		return cached;
	}
}

public class DefaultAdvisorChainFactory implements AdvisorChainFactory, Serializable {

    public List<Object> getInterceptorsAndDynamicInterceptionAdvice(
			Advised config, Method method, Class targetClass) {

		// This is somewhat tricky... we have to process introductions first,
		// but we need to preserve order in the ultimate list.
        // advisor链已经在config中持有了，这里可以直接使用
		List<Object> interceptorList = new ArrayList<Object>(config.getAdvisors().length);
		boolean hasIntroductions = hasMatchingIntroductions(config, targetClass);
        // 拦截器链是通过AdvisorAdapterRegistry来加入的，单例模式，默认是DefaultAdvisorAdapterRegistry
		AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();

        // 从当前ProxyFactoryBean中获取到的所有Advisor中进行选择
		for (Advisor advisor : config.getAdvisors()) {
            // 根据advisor的不同类型进行区分
			if (advisor instanceof PointcutAdvisor) {
				// Add it conditionally.
				PointcutAdvisor pointcutAdvisor = (PointcutAdvisor) advisor;
                // 切点增强的类是否是被代理的类
				if (config.isPreFiltered() || pointcutAdvisor.getPointcut().getClassFilter().matches(targetClass)) {   
                    // 一个Advisor封装的Advice可能既是一个BeforeAdvice，又是一个AfterAdvice，所以可能对应多个MethodInterceptor
					MethodInterceptor[] interceptors = registry.getInterceptors(advisor);
					MethodMatcher mm = pointcutAdvisor.getPointcut().getMethodMatcher();
                    // 使用MethodMatcher的matches方法进行匹配
					if (MethodMatchers.matches(mm, method, targetClass, hasIntroductions)) {
						if (mm.isRuntime()) { // 运行时匹配
							// Creating a new object instance in the getInterceptors() method
							// isn't a problem as we normally cache created chains.
							for (MethodInterceptor interceptor : interceptors) {
								interceptorList.add(new InterceptorAndDynamicMethodMatcher(interceptor, mm));
							}
						}
						else {
							interceptorList.addAll(Arrays.asList(interceptors));
						}
					}
				}
			}
			else if (advisor instanceof IntroductionAdvisor) {
				IntroductionAdvisor ia = (IntroductionAdvisor) advisor;
				if (config.isPreFiltered() || ia.getClassFilter().matches(targetClass)) {
					Interceptor[] interceptors = registry.getInterceptors(advisor);
					interceptorList.addAll(Arrays.asList(interceptors));
				}
			}
			else {
				Interceptor[] interceptors = registry.getInterceptors(advisor);
				interceptorList.addAll(Arrays.asList(interceptors));
			}
		}
		return interceptorList;
	}
}

public class DefaultAdvisorAdapterRegistry implements AdvisorAdapterRegistry, Serializable {

    private final List<AdvisorAdapter> adapters = new ArrayList<AdvisorAdapter>(3);

	/**
	 * Create a new DefaultAdvisorAdapterRegistry, registering well-known adapters.
	 * 是我们熟悉的几种Advice的适配器实现，其目标是将Advice对象适配成一个MethodInterceptor对象并提供一些其它功能
	 */
	public DefaultAdvisorAdapterRegistry() {
		registerAdvisorAdapter(new MethodBeforeAdviceAdapter());
		registerAdvisorAdapter(new AfterReturningAdviceAdapter());
		registerAdvisorAdapter(new ThrowsAdviceAdapter());
	}

    // 将一个Advice对象封装为一个Advisor
    public Advisor wrap(Object adviceObject) throws UnknownAdviceTypeException {
		if (adviceObject instanceof Advisor) {
			return (Advisor) adviceObject;
		}
		if (!(adviceObject instanceof Advice)) {
			throw new UnknownAdviceTypeException(adviceObject);
		}
		Advice advice = (Advice) adviceObject;
		if (advice instanceof MethodInterceptor) {
			// So well-known it doesn't even need an adapter.
			return new DefaultPointcutAdvisor(advice);
		}
		for (AdvisorAdapter adapter : this.adapters) {
			// Check that it is supported.
			if (adapter.supportsAdvice(advice)) {
				return new DefaultPointcutAdvisor(advice);
			}
		}
		throw new UnknownAdviceTypeException(advice);
	}
    
    // 一个advisor可能对应多个MethodInterceptor
    public MethodInterceptor[] getInterceptors(Advisor advisor) throws UnknownAdviceTypeException {
		List<MethodInterceptor> interceptors = new ArrayList<MethodInterceptor>(3);
		Advice advice = advisor.getAdvice();
		if (advice instanceof MethodInterceptor) {
			interceptors.add((MethodInterceptor) advice);
		}
        // 遍历在DefaultAdvisorAdapterRegistry中的AdvisorAdapter，
		for (AdvisorAdapter adapter : this.adapters) {
			if (adapter.supportsAdvice(advice)) {
                // 调用适配器中的getInterceptor方法将Advisor转化为MethodInterceptor
				interceptors.add(adapter.getInterceptor(advisor));
			}
		}
		if (interceptors.isEmpty()) {
			throw new UnknownAdviceTypeException(advisor.getAdvice());
		}
		return interceptors.toArray(new MethodInterceptor[interceptors.size()]);
	}
}

class MethodBeforeAdviceAdapter implements AdvisorAdapter, Serializable {

	public boolean supportsAdvice(Advice advice) {
		return (advice instanceof MethodBeforeAdvice);
	}

	public MethodInterceptor getInterceptor(Advisor advisor) {
		MethodBeforeAdvice advice = (MethodBeforeAdvice) advisor.getAdvice();
		return new MethodBeforeAdviceInterceptor(advice);
	}
    
}

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;
	}

	public Object invoke(MethodInvocation mi) throws Throwable {
        // 前置增强，增强之后继续执行ReflectiveMethodInvocation.proceed()进行之后的增强
		this.advice.before(mi.getMethod(), mi.getArguments(), mi.getThis() );
		return mi.proceed();
	}

}

class AfterReturningAdviceAdapter implements AdvisorAdapter, Serializable {

	public boolean supportsAdvice(Advice advice) {
		return (advice instanceof AfterReturningAdvice);
	}

	public MethodInterceptor getInterceptor(Advisor advisor) {
		AfterReturningAdvice advice = (AfterReturningAdvice) advisor.getAdvice();
		return new AfterReturningAdviceInterceptor(advice);
	}
}

public class AfterReturningAdviceInterceptor implements MethodInterceptor, AfterAdvice, Serializable {

	private final AfterReturningAdvice advice;


	/**
	 * Create a new AfterReturningAdviceInterceptor for the given advice.
	 * @param advice the AfterReturningAdvice to wrap
	 */
	public AfterReturningAdviceInterceptor(AfterReturningAdvice advice) {
		Assert.notNull(advice, "Advice must not be null");
		this.advice = advice;
	}

	public Object invoke(MethodInvocation mi) throws Throwable {
        // 先让原方法执行
		Object retVal = mi.proceed();
        // 原方法执行之后，返回值返回之前增强
		this.advice.afterReturning(retVal, mi.getMethod(), mi.getArguments(), mi.getThis());
		return retVal;
	}

}

@SuppressWarnings("serial")
class ThrowsAdviceAdapter implements AdvisorAdapter, Serializable {

	public boolean supportsAdvice(Advice advice) {
		return (advice instanceof ThrowsAdvice);
	}

	public MethodInterceptor getInterceptor(Advisor advisor) {
		return new ThrowsAdviceInterceptor(advisor.getAdvice());
	}

}

public class ThrowsAdviceInterceptor implements MethodInterceptor, AfterAdvice {

	private static final String AFTER_THROWING = "afterThrowing";

	private static final Log logger = LogFactory.getLog(ThrowsAdviceInterceptor.class);


	private final Object throwsAdvice;

	/** Methods on throws advice, keyed by exception class */
	private final Map<Class, Method> exceptionHandlerMap = new HashMap<Class, Method>();


	/**
	 * Create a new ThrowsAdviceInterceptor for the given ThrowsAdvice.
	 * @param throwsAdvice the advice object that defines the exception
	 * handler methods (usually a {@link org.springframework.aop.ThrowsAdvice}
	 * implementation)
	 */
	public ThrowsAdviceInterceptor(Object throwsAdvice) {
		Assert.notNull(throwsAdvice, "Advice must not be null");
		this.throwsAdvice = throwsAdvice;

		Method[] methods = throwsAdvice.getClass().getMethods();
		for (Method method : methods) {
			if (method.getName().equals(AFTER_THROWING) &&
					(method.getParameterTypes().length == 1 || method.getParameterTypes().length == 4) &&
					Throwable.class.isAssignableFrom(method.getParameterTypes()[method.getParameterTypes().length - 1])
				) {
				// Have an exception handler
				this.exceptionHandlerMap.put(method.getParameterTypes()[method.getParameterTypes().length - 1], method);
				if (logger.isDebugEnabled()) {
					logger.debug("Found exception handler method: " + method);
				}
			}
		}

		if (this.exceptionHandlerMap.isEmpty()) {
			throw new IllegalArgumentException(
					"At least one handler method must be found in class [" + throwsAdvice.getClass() + "]");
		}
	}

	public int getHandlerMethodCount() {
		return this.exceptionHandlerMap.size();
	}

	/**
	 * Determine the exception handle method. Can return null if not found.
	 * @param exception the exception thrown
	 * @return a handler for the given exception type
	 */
	private Method getExceptionHandler(Throwable exception) {
		Class exceptionClass = exception.getClass();
		if (logger.isTraceEnabled()) {
			logger.trace("Trying to find handler for exception of type [" + exceptionClass.getName() + "]");
		}
		Method handler = this.exceptionHandlerMap.get(exceptionClass);
		while (handler == null && !exceptionClass.equals(Throwable.class)) {
			exceptionClass = exceptionClass.getSuperclass();
			handler = this.exceptionHandlerMap.get(exceptionClass);
		}
		if (handler != null && logger.isDebugEnabled()) {
			logger.debug("Found handler for exception of type [" + exceptionClass.getName() + "]: " + handler);
		}
		return handler;
	}

	public Object invoke(MethodInvocation mi) throws Throwable {
        // try-catch包装，proceed方法之后执行过程中如果抛出了异常，先调用ThrowsAdvice中的回调方法，之后将此异常向上抛出
		try {
			return mi.proceed();
		}
		catch (Throwable ex) {
			Method handlerMethod = getExceptionHandler(ex);
			if (handlerMethod != null) {
				invokeHandlerMethod(mi, ex, handlerMethod);
			}
			throw ex;
		}
	}

	private void invokeHandlerMethod(MethodInvocation mi, Throwable ex, Method method) throws Throwable {
		Object[] handlerArgs;
		if (method.getParameterTypes().length == 1) {
			handlerArgs = new Object[] { ex };
		}
		else {
			handlerArgs = new Object[] {mi.getMethod(), mi.getArguments(), mi.getThis(), ex};
		}
		try {
            // 反射调用ThrowsAdvice中的回调方法
			method.invoke(this.throwsAdvice, handlerArgs);
		}
		catch (InvocationTargetException targetEx) {
			throw targetEx.getTargetException();
		}
	}

}

<!--定义advise sayhelloadvice定义了通知包含什么-->
<bean id="sayhelloadvice" class="mytests.aopTests.SayHelloBeforemale"/>

<!--waiter定义了在何时(调用proxyInterfaces接口的方法时)为什么对象(target指定，此对象需要实现proxyInterfaces接口)-->
<!--应用何种通知(interceptorNames中指定)-->
<!-- 定义advisor-->
<bean id="waiter" class="org.springframework.aop.framework.ProxyFactoryBean">   
    <property name="target">
        <bean class="mytests.aopTests.Waiter"/>
    </property>
    <property name="interceptorNames">
        <list>
            <value>sayhelloadvice</value>
            <value>sayhelloadvice</value>
        </list>
    </property>
</bean>

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd">
    
    <bean id="sayhelloadvice" class="mytests.aopTests.SayHelloBeforemale"/>
    <bean id="waiter" class="mytests.aopTests.Waiter"/>
    
    <aop:config>
        <aop:aspect ref = "sayhelloadvice">
            <aop:before pointcut="execution(* mytests.aopTests.Waiter.say*(..))" method="before"></aop:before>
            <aop:after-returning pointcut="execution(* mytests.aopTests.Waiter.say*(..))" method="afterReturning"></aop:after-returning>
        </aop:aspect>
    </aop:config>

    <!--
    通过aop命名空间的<aop:aspectj-autoproxy />声明自动为spring容器中那些配置@aspectJ切面的bean创建代理，织入切面。当然，spring
    在内部依旧采用AnnotationAwareAspectJAutoProxyCreator进行自动代理的创建工作，但具体实现的细节已经被<aop:aspectj-autoproxy />
    隐藏起来了，对这个自定义标签的处理的主要任务就是在WAC中注册一个BeanPostProcessor，也就是AnnotationAwareAspectJAutoProxyCreator类的实例对象，之后使用这个processor对符合切面要求的bean进行代理增强。
    具体处理过程可参考：https://blog.csdn.net/heroqiang/article/details/79037741，
    注意父WAC中的切面可以对子WAC中的bean进行增强，子WAC中的切面不能对父WAC中的bean进行增强。  
    -->
    <!--<aop:aspectj-autoproxy/>-->    

</beans>

public abstract class AbstractAutoProxyCreator extends ProxyConfig
		implements SmartInstantiationAwareBeanPostProcessor, BeanClassLoaderAware, BeanFactoryAware,
		Ordered, AopInfrastructureBean {

    /**
	 * Create a proxy with the configured interceptors if the bean is
	 * identified as one to proxy by the subclass.
	 * @see #getAdvicesAndAdvisorsForBean
	 * 对bean进行后置处理
	 */
	public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
		if (bean != null) {
			Object cacheKey = getCacheKey(bean.getClass(), beanName);
			if (!this.earlyProxyReferences.containsKey(cacheKey)) {
                // 判断是否有必要对bean进行代理
				return wrapIfNecessary(bean, beanName, cacheKey);
			}
		}
		return bean;
	}

    /**
	 * Wrap the given bean if necessary, i.e. if it is eligible for being proxied.
	 * @param bean the raw bean instance
	 * @param beanName the name of the bean
	 * @param cacheKey the cache key for metadata access
	 * @return a proxy wrapping the bean, or the raw bean instance as-is
	 */
	protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
		if (beanName != null && this.targetSourcedBeans.containsKey(beanName)) {
			return bean;
		}
		if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
			return bean;
		}
		if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
			this.advisedBeans.put(cacheKey, Boolean.FALSE);
			return bean;
		}

		// Create proxy if we have advice.
		Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
		if (specificInterceptors != DO_NOT_PROXY) {
			this.advisedBeans.put(cacheKey, Boolean.TRUE);
            // 实际产生代理对象的方法
			Object proxy = createProxy(bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
			this.proxyTypes.put(cacheKey, proxy.getClass());
			return proxy;
		}

		this.advisedBeans.put(cacheKey, Boolean.FALSE);
		return bean;
	}

    /**
	 * Create an AOP proxy for the given bean.
	 * @param beanClass the class of the bean
	 * @param beanName the name of the bean
	 * @param specificInterceptors the set of interceptors that is
	 * specific to this bean (may be empty, but not null)
	 * @param targetSource the TargetSource for the proxy,
	 * already pre-configured to access the bean
	 * @return the AOP proxy for the bean
	 * @see #buildAdvisors	 
	 */
	protected Object createProxy(
			Class<?> beanClass, String beanName, Object[] specificInterceptors, TargetSource targetSource) {

        // 可见实际上还是使用了ProxyFactory来产生的代理对象
		ProxyFactory proxyFactory = new ProxyFactory();
		// Copy our properties (proxyTargetClass etc) inherited from ProxyConfig.
		proxyFactory.copyFrom(this);

		if (!shouldProxyTargetClass(beanClass, beanName)) {
			// Must allow for introductions; can't just set interfaces to
			// the target's interfaces only.
			Class<?>[] targetInterfaces = ClassUtils.getAllInterfacesForClass(beanClass, this.proxyClassLoader);
			for (Class<?> targetInterface : targetInterfaces) {
				proxyFactory.addInterface(targetInterface);
			}
		}

		Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
		for (Advisor advisor : advisors) {
			proxyFactory.addAdvisor(advisor);
		}

		proxyFactory.setTargetSource(targetSource);
		customizeProxyFactory(proxyFactory);

		proxyFactory.setFrozen(this.freezeProxy);
		if (advisorsPreFiltered()) {
			proxyFactory.setPreFiltered(true);
		}

		return proxyFactory.getProxy(this.proxyClassLoader);
	}
}