jdkproxy的简易实现

 1.实现类

public class CustomInvocationHandle implements InvocationHandler {
    private Object target;//目标类

    public CustomInvocationHandle(Object o){
        this.target=o;
    }
    //生成代理对象的方法
    public Object createProxy(){
        //jdk提供了Proxy类 有一个方法专门用来生成代理类对象
        Object proxy= Proxy.newProxyInstance(CustomInvocationHandle.class.getClassLoader(),target.getClass().getInterfaces(),this);
        return proxy;
    }
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        //前置增强 解析表达式,
        if (method.getName().indexOf("say")>=0){
            showTime();
        }

        Object returnValue=method.invoke(target,args);

        return returnValue;
    }

    private void showTime() {
        System.out.println("时间："+new Date());
    }
}

2.测试前置增强（代理对象调方法前置增强，输出时间）

 //System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles","true");
        //配置将代理类的字节码保存到本地

        Hello target=new HelloImpl();//目标类

        CustomInvocationHandle handle=new CustomInvocationHandle(target);

        Object proxy = handle.createProxy();
        System.out.println(proxy);
        Hello hi=(Hello)proxy;
        hi.sayHello();
        hi.sayBye();