一、Spring抽象出了AopProxy接口，用处：
1）用来抽象JDK和Cglib
2）暗示统一了他们的自调用行为：调用Target的方法。
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Note：CGlib可以实现自调用时走代理对象，但是Spring统一了动态代理的规则，使其和jdk的动态代理保持一致，致使程序在使用不同的代理时能表现一致。（非不能也，实不为也。）
二、CglibAopProxy源码
从以下代码的路径中可以发现，Cglib使用methodProxy.invoke(target, argsToUse)而非methodProxy.invoke(proxy, argsToUse)，来保持和jdk动态代理同样的逻辑。
- 位置：org.springframework.aop.framework.CglibAopProxy.DynamicAdvisedInterceptor#intercept
public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
Object oldProxy = null;
boolean setProxyContext = false;
Class targetClass = null;
Object target = null;
try {
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 = getTarget();
if (target != null) {
targetClass = target.getClass();
}
List位置：org.springframework.aop.framework.CglibAopProxy.CglibMethodInvocation
private static class CglibMethodInvocation extends ReflectiveMethodInvocation {
private final MethodProxy methodProxy;
private final boolean publicMethod;
public CglibMethodInvocation(Object proxy, Object target, Method method, Object[] arguments,
Class targetClass, List位置：org.springframework.aop.support.AopUtils#invokeJoinpointUsingReflection
public static Object invokeJoinpointUsingReflection(Object target, Method method, Object[] args)
throws Throwable {
// Use reflection to invoke the method.
try {
ReflectionUtils.makeAccessible(method);
return method.invoke(target, args);
}
catch (InvocationTargetException ex) {
// Invoked method threw a checked exception.
// We must rethrow it. The client won't see the interceptor.
throw ex.getTargetException();
}
catch (IllegalArgumentException ex) {
throw new AopInvocationException("AOP configuration seems to be invalid: tried calling method [" +
method + "] on target [" + target + "]", ex);
}
catch (IllegalAccessException ex) {
throw new AopInvocationException("Could not access method [" + method + "]", ex);
}
}