Spring-AOP源码探讨-创建bean代理对象&代理方法执行流程

在上一篇中梳理了匹配bean通知(Advisor)的流程。
这篇延续上篇，梳理创建bean代理对象源码。

先回顾下AbstractAutoProxyCreator类的wrapIfNecessary方法：

/**
 * 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) {
	...
	// Create proxy if we have advice.
	//获取目标bean的各种增强
	Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
	if (specificInterceptors != DO_NOT_PROXY) {
		this.advisedBeans.put(cacheKey, Boolean.TRUE);
		//创建代理对象
		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;
}

跟着createProxy(bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean))方法：

protected Object createProxy(Class beanClass, @Nullable String beanName,
			@Nullable Object[] specificInterceptors, TargetSource targetSource) {

		if (this.beanFactory instanceof ConfigurableListableBeanFactory) {
			AutoProxyUtils.exposeTargetClass((ConfigurableListableBeanFactory) this.beanFactory, beanName, beanClass);
		}

		ProxyFactory proxyFactory = new ProxyFactory();
		proxyFactory.copyFrom(this);

		if (!proxyFactory.isProxyTargetClass()) {
			if (shouldProxyTargetClass(beanClass, beanName)) {
				proxyFactory.setProxyTargetClass(true);
			}
			else {
				evaluateProxyInterfaces(beanClass, proxyFactory);
			}
		}

		Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
		proxyFactory.addAdvisors(advisors);
		proxyFactory.setTargetSource(targetSource);
		customizeProxyFactory(proxyFactory);

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

		return proxyFactory.getProxy(getProxyClassLoader());
	}

代理对象的创建通过ProxyFactory工厂类的getProxy方法创建：

public Object getProxy(@Nullable ClassLoader classLoader) {
		return createAopProxy().getProxy(classLoader);
	}

这里需要根据配置使用不同的AopProxy代理方式创建代理对象，分别是JDK动态代理或CGlib代理。
ProxyCreatorSupport#createAopProxy：

protected final synchronized AopProxy createAopProxy() {
	if (!this.active) {
		activate();
	}
	return getAopProxyFactory().createAopProxy(this);
}

AopProxyFactory默认实现类是DefaultAopProxyFactory：

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)) {
			//JDK动态代理
			return new JdkDynamicAopProxy(config);
		}
		//Cglib代理
		return new ObjenesisCglibAopProxy(config);
	}
	else {
		return new JdkDynamicAopProxy(config);
	}
}

这里以JdkDynamicAopProxy类为例，看看其getProxy方法：

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

最终是调用Proxy类的newProxyInstance方法创建代理对象。

JdkDynamicAopProxy类本身实现了InvocationHandler接口，其invoke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;
	Object target = null;

	try {
		if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) {
			// The target does not implement the equals(Object) method itself.
			return equals(args[0]);
		}
		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);
		}
		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;

		if (this.advised.exposeProxy) {
			// Make invocation available if necessary.
			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.
		target = targetSource.getTarget();
		Class targetClass = (target != null ? target.getClass() : null);

		// Get the interception chain for this method.
		//获取拦截器链，也就是MethodInterceptor，前面的PointcutAdvisor封装的实例
		List