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() failed
throw new AopConfigException("Unexpected AOP exception", ex);
}
}