spring aop(五)--ProxyFactoryBean创建代理的实现

先看看ProxyFactoryBean的类层次结构.

ProxyFactoryBean实现了FactoryBean,最终通过getObject方法生成Bean,所以getObject方法是个入口.

public Object getObject() throws BeansException {initializeAdvisorChain();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();}}

1.配置的Advisor链就是在initializeAdvisorChain()完成的,主要工作是将所有Advice Bean加入到父类AdvisedSupport的advisors List变量.Bean的作用范围来分为singleton,prototype(web环境下,还有request,session,application),不同的作用范围生成Bean的方式不同.
2.再看getSingletonInstance()

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.Class<?> targetClass = getTargetClass();if (targetClass == null) {throw new FactoryBeanNotInitializedException("Cannot determine target class for proxy");}setInterfaces(ClassUtils.getAllInterfacesForClass(targetClass, this.proxyClassLoader));}// Initialize the shared singleton instance.super.setFrozen(this.freezeProxy);this.singletonInstance = getProxy(createAopProxy());}return this.singletonInstance;}

如果实例化过了,直接返回.这个方法最关键是this.singletonInstance = getProxy(createAopProxy());这个singletonInstance是我们最终返回的实例.
org.springframework.aop.framework.ProxyCreatorSupport#createAopProxy

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

getAopProxyFactory()返回的是AopProxyFactory,只有一个实现DefaultAopProxyFactory,所以只要去看org.springframework.aop.framework.DefaultAopProxyFactory#createAopProxy,到底是基于JDK生成还是基于CGLib生成代理,由这个方法决定.

a.假设createAopProxy()返回的是JdkDynamicAopProxy,看看org.springframework.aop.framework.JdkDynamicAopProxy#getProxy(java.lang.ClassLoader)

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);}

终于看到熟悉的Proxy.newProxyInstance了吧!

b.那继续看看org.springframework.aop.framework.CglibAopProxy#getProxy(java.lang.ClassLoader)

public Object getProxy(ClassLoader classLoader) {if (logger.isDebugEnabled()) {logger.debug("Creating CGLIB proxy: target source is " + this.advised.getTargetSource());}try {Class<?> rootClass = this.advised.getTargetClass();Assert.state(rootClass != null, "Target class must be available for creating a CGLIB proxy");Class<?> proxySuperClass = rootClass;if (ClassUtils.isCglibProxyClass(rootClass)) {proxySuperClass = rootClass.getSuperclass();Class<?>[] additionalInterfaces = rootClass.getInterfaces();for (Class<?> additionalInterface : additionalInterfaces) {this.advised.addInterface(additionalInterface);}}// Validate the class, writing log messages as necessary.validateClassIfNecessary(proxySuperClass, classLoader);//配置CGLIB Enhancer...Enhancer enhancer = createEnhancer();if (classLoader != null) {enhancer.setClassLoader(classLoader);if (classLoader instanceof SmartClassLoader &&((SmartClassLoader) classLoader).isClassReloadable(proxySuperClass)) {enhancer.setUseCache(false);}}enhancer.setSuperclass(proxySuperClass);enhancer.setInterfaces(AopProxyUtils.completeProxiedInterfaces(this.advised));enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);enhancer.setStrategy(new UndeclaredThrowableStrategy(UndeclaredThrowableException.class));//获取回调Callback[] callbacks = getCallbacks(rootClass);Class<?>[] types = new Class<?>[callbacks.length];for (int x = 0; x < types.length; x++) {types[x] = callbacks[x].getClass();}enhancer.setCallbackFilter(new ProxyCallbackFilter(this.advised.getConfigurationOnlyCopy(), this.fixedInterceptorMap, this.fixedInterceptorOffset));enhancer.setCallbackTypes(types);//生成代理类与代理实例return createProxyClassAndInstance(enhancer, callbacks);}catch (CodeGenerationException ex) {throw new AopConfigException("Could not generate CGLIB subclass of class [" +this.advised.getTargetClass() + "]: " +"Common causes of this problem include using a final class or a non-visible class",ex);}catch (IllegalArgumentException ex) {throw new AopConfigException("Could not generate CGLIB subclass of class [" +this.advised.getTargetClass() + "]: " +"Common causes of this problem include using a final class or a non-visible class",ex);}catch (Exception ex) {// TargetSource.getTarget() failedthrow new AopConfigException("Unexpected AOP exception", ex);}}