JAVA 代理 动态代理 Proxy

* 代理必须持有被代理的对象，而且还必须跟被代理对象实现相同的接口

* 不管是静态代理还是动态代理都必须满足以上2个规则

 

代理的作用：

能够在不改变原来代码的逻辑的情况下增加代码功能

 

基于以上2个原则，所以代理和非代理才能达到相同的目的

 

1.静态代理 静态代理只能代理一个对象，

优点：代码逻辑清晰简单 

例如下面就只能代理Star

 

public class StaticProxy implements Star{

 

private Star star;

public Star getStar() {

return star;

}

 

public void setStar(Star star) {

this.star = star;

}

 

@Override

public String sing(String musicName) {

//增强

System.out.println("增强开始");

String result= star.sing(musicName);

System.out.println("增强结束");

//增强结束

return result;

}

 

@Override

public String dance(String danceName) {

//增强

System.out.println("增强开始");

String result= star.dance(danceName);

System.out.println("增强结束");

//增强结束

return result;

}

}

 

 

2.动态代理，可以代理各种对象，必须要实现implements InvocationHandler

缺点：代码逻辑稍微绕了点

 

public class MyProxy implements InvocationHandler {

 

// 目标类，也就是被代理对象

private Object target;

 

public void setTarget(Object target) {

this.target = target;

}

 

/**

* 可以做增强

*/

public Object invoke(Object proxy, Method method, Object[] args)

throws Throwable {

System.out.println("收钱");

Object result = method.invoke(target, args);//调用代理

return result;

}

 

}

 

动态 代理工具类

public class ProxyUtil {

 

public static Object CreatProxyedObj(Object target,InvocationHandler h)

{

return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), h);

}

 

 

}

 

 

测试类

public class TestProxy {

 

public static void main(String[] args) {

Star ldh = new HongKongStar();

MyProxy starProxy = new MyProxy();

starProxy.setTarget(ldh);

Star proxy = (Star) ProxyUtil.CreatProxyedObj(ldh, starProxy);

proxy.sing("今天");

proxy.dance("开心的马六");

CrmDao dao = new CrmDaoImpl();

MyProxy daoProxy = new MyProxy();

daoProxy.setTarget(dao);

CrmDao crmDao =(CrmDao) ProxyUtil.CreatProxyedObj(dao, daoProxy);

crmDao.delete(1);

crmDao.queryById(1);

crmDao.update(1);

}

}

 

 

public interface Star {

 

public String sing(String musicName);

public String dance(String danceName);

}

 

package com.asiainfo.zy;

 

public class HongKongStar implements Star{

 

@Override

public String sing(String musicName) {

System.out.println("准备开始唱"+musicName);

try {

Thread.sleep(1000);

} catch (InterruptedException e) {

e.printStackTrace();

}

System.out.println("唱歌结束");

return musicName;

}

 

@Override

public String dance(String danceName) {

System.out.println("音乐响起，准备开始跳舞"+danceName);

try {

Thread.sleep(1000);

} catch (InterruptedException e) {

e.printStackTrace();

}

System.out.println("跳舞结束");

return danceName;

}

 

}