Spring AOP直白的来说就是使用了JDK的动态代理和CGLIB对Bean的代理，从而实现方法增强的效果。
注意：
1.分析框架代码时，要常使用类继承、调用关系等快捷键，可以更高效的学习，快捷键可以设置成你习惯的按键；
2.本文重在怎么自我分析框架代码，所以对其中解析需自己实际跟踪代码实践方可；
3.spring源代码版本 spring-framework-3.2.1.RELEASE。
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory，自动装箱BeanFactory。
org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator，代理对象创建类。
org.springframework.aop.framework.JdkDynamicAopProxy，JDK动态代理类。
org.springframework.aop.framework.CglibAopProxy，CGLIB动态代理类。
入口-createBean
前面我们分析Spring IOC时，了解了IOC的资源定位、加载、注册等步骤，但是对于AOP的实现还未分析。
还记得createBean嘛，这里就是实际创建Bean的入口，在getBean中调用了。
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory
public <T> T createBean(Class<T> beanClass) throws BeansException {
// Use prototype bean definition, to avoid registering bean as dependent bean.
RootBeanDefinition bd = new RootBeanDefinition(beanClass);
bd.setScope(SCOPE_PROTOTYPE);
bd.allowCaching = false;
return (T) createBean(beanClass.getName(), bd, null);
}protected Object createBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
throws BeanCreationException {
if (logger.isDebugEnabled()) {
logger.debug("Creating instance of bean '" + beanName + "'");
}
// Make sure bean class is actually resolved at this point.
resolveBeanClass(mbd, beanName);
// Prepare method overrides.
try {
mbd.prepareMethodOverrides();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(mbd.getResourceDescription(),
beanName, "Validation of method overrides failed", ex);
}
try {
// 产生 AOP 代理对象的入口
Object bean = resolveBeforeInstantiation(beanName, mbd);
if (bean != null) {
return bean;
}
}
catch (Throwable ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"BeanPostProcessor before instantiation of bean failed", ex);
}
Object beanInstance = doCreateBean(beanName, mbd, args);
if (logger.isDebugEnabled()) {
logger.debug("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
}
在对象实例化前做相应的逻辑处理，即是否需创建代理对象
protected Object applyBeanPostProcessorsBeforeInstantiation(Class beanClass, String beanName)
throws BeansException {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
// 在对象实例化前的处理操作
Object result = ibp.postProcessBeforeInstantiation(beanClass, beanName);
if (result != null) {
return result;
}
}
}
return null;
}
<strong> </strong>public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
Object cacheKey = getCacheKey(beanClass, beanName);
if (beanName == null || !this.targetSourcedBeans.containsKey(beanName)) {
if (this.advisedBeans.containsKey(cacheKey)) {
return null;
}
if (isInfrastructureClass(beanClass) || shouldSkip(beanClass, beanName)) {
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return null;
}
}
// Create proxy here if we have a custom TargetSource.
// Suppresses unnecessary default instantiation of the target bean:
// The TargetSource will handle target instances in a custom fashion.
if (beanName != null) {
TargetSource targetSource = getCustomTargetSource(beanClass, beanName);
if (targetSource != null) {
this.targetSourcedBeans.put(beanName, Boolean.TRUE);
// 获取通知点即需增强效果的接口，如想了解可查看其子类AbstractAdvisorAutoProxyCreator
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
// 根据类名、需增强接口等信息创建代理对象
Object proxy = createProxy(beanClass, beanName, specificInterceptors, targetSource);
this.proxyTypes.put(cacheKey, proxy.getClass());
return proxy;
}
}
return null;
}
接下来将看到一系列的准备工作：代理工厂、目标对象的接口、目标对象的通知者等。
<span style="white-space:pre"> </span>protected Object createProxy(
Class<?> beanClass, String beanName, Object[] specificInterceptors, TargetSource targetSource) {
ProxyFactory proxyFactory = new ProxyFactory();
// Copy our properties (proxyTargetClass etc) inherited from ProxyConfig.
proxyFactory.copyFrom(this);
if (!shouldProxyTargetClass(beanClass, beanName)) {
// 获取所有目标对象的接口
Class<?>[] targetInterfaces = ClassUtils.getAllInterfacesForClass(beanClass, this.proxyClassLoader);
for (Class<?> targetInterface : targetInterfaces) {
proxyFactory.addInterface(targetInterface);
}
}
// 通过通知点即类名创建通知者(切入点及增强效果的集合)
Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
for (Advisor advisor : advisors) {
proxyFactory.addAdvisor(advisor);
}
proxyFactory.setTargetSource(targetSource);
customizeProxyFactory(proxyFactory);
proxyFactory.setFrozen(this.freezeProxy);
if (advisorsPreFiltered()) {
proxyFactory.setPreFiltered(true);
}
// 通过工厂和proxyClassLoader来获取代理对象
return proxyFactory.getProxy(this.proxyClassLoader);
}
<span style="white-space:pre"> </span>public Object getProxy(ClassLoader classLoader) {
return createAopProxy().getProxy(classLoader); //使用
}创建JdkDynamicAopProxy还是CglibProxyFactory。
其中JDK的动态代理只能对接口型的目标对象进行代理，而CGLIB没有此限制，代码中我们可以明确的看到。
<span style="white-space:pre"> </span>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()) { // 目标对象若是接口，即生产JDK的动态代理
return new JdkDynamicAopProxy(config);
}
return CglibProxyFactory.createCglibProxy(config); // 非接口型目标对象，即使用CGLIB来实现代理。
}
else {
return new JdkDynamicAopProxy(config);
}
}接下来就是的getProxy生产代理对象就要看JdkDynamicAopProxy和CglibProxyFactory两个类了，若对两者的动态代理不熟悉，先实现了解下，
再接着分析。
JDK动态代理：http://blog.csdn.net/xiaohai0504/article/details/6884925
CGLIB动态代理：http://blog.csdn.net/xiaohai0504/article/details/6832990
原文地址：http://blog.csdn.net/hai8902882/article/details/39503043
