Spring如何基于Proxy及cglib实现动态代理

spring中提供了两种动态代理的方式，分别是Java Proxy以及cglib

JavaProxy只能代理接口，而cglib是通过继承的方式，实现对类的代理

添加一个接口以及对应的实现类

public interface HelloInterface { void sayHello();}

public class HelloInterfaceImpl implements HelloInterface { @Override public void sayHello() { System.out.println('hello'); }}

JavaProxy通过实现InvocationHandler实现代理

public class CustomInvocationHandler implements InvocationHandler { private HelloInterface helloInterface; public CustomInvocationHandler(HelloInterface helloInterface) { this.helloInterface = helloInterface; } @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { System.out.println('before hello for proxy'); Object result = method.invoke(helloInterface, args); System.out.println('after hello for proxy'); return result; }}

而cglib实现MethodInterceptor进行方法上的代理

public class CustomMethodInterceptor implements MethodInterceptor { @Override public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable { System.out.println('before hello for cglib'); Object result = methodProxy.invokeSuper(o, objects); System.out.println('after hello for cglib'); return result; }}

分别实现调用代码

public static void main(String[] args) { Enhancer enhancer = new Enhancer(); enhancer.setSuperclass(HelloInterfaceImpl.class); enhancer.setCallback(new CustomMethodInterceptor()); HelloInterface target = (HelloInterface) enhancer.create(); target.sayHello(); CustomInvocationHandler invocationHandler = new CustomInvocationHandler(new HelloInterfaceImpl()); HelloInterface target2 = (HelloInterface) Proxy.newProxyInstance(Demo.class.getClassLoader(), new Class[]{HelloInterface.class}, invocationHandler); target2.sayHello(); }

可以看到对于的代理信息输出

before hello for cglibhelloafter hello for cglibbefore hello for proxyhelloafter hello for proxy

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