1 、 ProxyFactoryBean 把 proxy 的創建交給 AopProxy 去做。

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2. 、那么 AopProxy 又如何獲取？答案是從 AopProxyFactory 獲得。這個 AopProxyFactory 已在 ProxyFactoryBean 掌控范圍內，如上述代碼所示。 AopProxyFactory interface 如下所示：

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3、AopProxy是如何introduce Advised interface的？那要先從AopProxyFactory的implementation說起。

AopProxyFactory 的實現類目前只有 DefaultAopProxyFactory 。這個類的核心方法如下：

???????????

?? 這個方法主要是依賴 CglibProxyFactory 類和 JdkDynamicAopProxy 類。這兩個類是如何代理所有的接口的呢？

這兩個類都是重要接口 AopProxy 的實現類，這個接口的核心方法是

??????????? public Object getProxy(ClassLoader classLoader) 。

其中 JdkDynamicAopProxy 實現該方法用到的獲取需要代理的接口的代碼如下：

??????????

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而 CglibProxyFactory 的 getProxy(ClassLoader classLoader) 方法如下：

??????????

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從上面可以看出，這兩個 AopProxy 實現方案在獲取接口時都是通過 AopProxyUtils.completeProxiedInterfaces(this.advised) 獲取的。該方法如下：

??????????? /**

??????????? ?* Get complete set of interfaces to proxy. This will always add the Advised interface

??????????? ?* unless the AdvisedSupport's "opaque" flag is true.

??????????? ?* @return the complete set of interfaces to proxy

??????????? ?*/

???????????

從這可以看出，是在這強制加了對 Advised? interface 的實現。前提是是否允許代理該 interafce ，這由 isOpaque 方法確定，該方法 Return whether proxies created by this configuration should be prevented from being cast to Advised.

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4. 順便提一下， Advised interface 的具體實現又是怎樣的，在哪呢？

4.1 在 JdkDynamicAopProxy 里，

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??????????? public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

……

??????????????????????? ??????????? if (Advised.class == method.getDeclaringClass()) {

??????????????????????? ??????????? ??????????? // service invocations on ProxyConfig with the proxy config

??????????????????????? ??????????? ??????????? return AopUtils.invokeJoinpointUsingReflection(this.advised, method, args);

??????????????????????? ??????????? }

……

}

注意第一個參數是 this.advised ， 其實就是 ProxyFactoryBean 本身，注意在我發表的其天的 Spring 文章里也曾提到， ProxyFactoryBean extends AdvisedSupport ，

而 AdisedSupport extends ProxyConfig implements Advised ，也就是說 Advised 的默認實現就是 AdisedSupport 。

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4.2 在 Cglib2AopProxy 里（如果不熟 Cglib ，建議先看看其天有關的 Cglib 資料），

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??????????? public Object getProxy(ClassLoader classLoader) {

……

Enhancer enhancer = new Enhancer();

……

enhancer.setCallbackFilter(new ProxyCallbackFilter(this.advised));

……

Callback[] callbacks = getCallbacks(rootClass);

……

……

……

}

private Callback[] getCallbacks(Class rootClass) throws Exception {

……

??????????? ??????????? Callback[] mainCallbacks = new Callback[]{

??????????????????????? ??????????? aopInterceptor, // for normal advice

??????????????????????? ??????????? targetInterceptor, // invoke target without considering advice, if optimized

??????????????????????? ??????????? new SerializableNoOp(), // no override for methods mapped to this

??????????????????????? ??????????? targetDispatcher, this.advisedDispatcher,

??????????????????????? ??????????? new EqualsInterceptor(this.advised)

??????????? ??????????? };

……

}

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private class ProxyCallbackFilter implements CallbackFilter {

public int accept(Method method) {

??????????????????????? ??????????? if (method.getDeclaringClass() == Advised.class) {

??????????????????????? ??????????? ??????????? if (logger.isDebugEnabled()) {

??????????????????????? ??????????????????????? ??????????? logger.debug("Method " + method + " is declared on Advised - using DISPATCH_ADVISED");

??????????????????????? ????????????????????? }

??????????????????????? ??????????? ??????????? return DISPATCH_ADVISED;// DISPATCH_ADVISED 值為 4.

??????????????????????? ??????????? }

……

}

}

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private final transient AdvisedDispatcher advisedDispatcher = new AdvisedDispatcher();

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??????????? /**

??????????? ?* Dispatcher for any methods declared on the Advised class.

??????????? ?*/

??????????? private class AdvisedDispatcher implements Dispatcher, Serializable {

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??????????? ??????????? public Object loadObject() throws Exception {

??????????????????????? ??????????? return advised;

????????????????????? }

??????????? }

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注意 Dispatcher extends Callback interface 。