Spring 创建 JDK- and CGLIB-based proxies的区别

几条原则：

1.  If the class of a target object that is to be proxied (hereafter simply referred to as the target class) doesn't implement any interfaces, then a CGLIB-based proxy will be created.【原因是：This is the easiest scenario, because JDK proxies are interface based, and no interfaces means JDK proxying isn't even possible. 】
2. If the proxyTargetClass property of the ProxyFactoryBean has been set to true, then a CGLIB-based proxy will be created. 【无视ProxyFactoryBean的属性proxyInterfaces是否有设置成为某一个或多个接口名】
3. If the proxyInterfaces property of the ProxyFactoryBean has been set to one or more fully qualified interface names, then a JDK-based proxy will be created.
   
4. If the proxyInterfaces property of the ProxyFactoryBean has not been set but the target class does implement one (or more) interfaces, then the ProxyFactoryBean will auto-detect the fact that the target class does actually implement at least one interface, and a JDK-based proxy will be created, or a CGLIB-based proxy will be created.【如果是JDK代理这一条和第三条行为一致】