public Object getProxy(ClassLoader classLoader) { return createAopProxy().getProxy(classLoader); } // createAopProxy()方法就是决定究竟创建何种类型的proxy protected final synchronized AopProxy createAopProxy() { if (!this.active) { activate(); } // 关键方法createAopProxy() return getAopProxyFactory().createAopProxy(this); } // createAopProxy() public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException { // 1.config.isOptimize()是否使用优化的代理策略，目前使用与CGLIB // config.isProxyTargetClass() 是否目标类本身被代理而不是目标类的接口 // hasNoUserSuppliedProxyInterfaces()是否存在代理接口 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."); } // 2.如果目标类是接口类（目标对象实现了接口），则直接使用JDKproxy if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) { return new JdkDynamicAopProxy(config); } // 3.其他情况则使用CGLIBproxy return new ObjenesisCglibAopProxy(config); } else { return new JdkDynamicAopProxy(config); } }复制代码
getProxy()方法
final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable// JdkDynamicAopProxy类结构，由此可知，其实现了InvocationHandler，则必定有invoke方法，来被调用，也就是用户调用bean相关方法时，此invoke()被真正调用 // getProxy() 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, true); findDefinedEqualsAndHashCodeMethods(proxiedInterfaces); // JDK proxy 动态代理的标准用法 return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this); }复制代码
invoke()方法法
//使用了JDK动态代理模式，真正的方法执行在invoke()方法里，看到这里在想一下上面动态代理的例子，是不是就完全明白Spring源码实现动态代理的原理了。 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 { // 1.以下的几个判断，主要是为了判断method是否为equals、hashCode等Object的方法 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; } // May be null. Get as late as possible to minimize the time we "own" the target, // in case it comes from a pool. target = targetSource.getTarget(); if (target != null) { targetClass = target.getClass(); } // 2.获取当前bean被拦截方法链表 List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass); // 3.如果为空，则直接调用target的method if (chain.isEmpty()) { Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args); retVal = AopUtils.invokeJoinpointUsingReflection(target, method, argsToUse); } // 4.不为空，则逐一调用chain中的每一个拦截方法的proceed，这里的一系列执行的原因以及proceed执行的内容，我 在这里就不详细讲了，大家感兴趣可以自己去研读哈 else { // We need to create a method invocation... invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain); // Proceed to the joinpoint through the interceptor chain. retVal = invocation.proceed(); } ... return retVal; } } }
