代理模式-JDK Proxy

使用JDK支持的代理模式, 动态代理

场景如下: 本文例子代理了ArrayList, 在ArrayList每次操作时, 在操作之前和之后都进行一些额外的操作.

ArrayListProxy类

这里是代理的实现.

import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;public class ArrayListProxy implements InvocationHandler {    private Object proxy;    public ArrayListProxy(Object obj) {        this.proxy = obj;    }    @Override    public Object invoke(Object proxy, Method method, Object[] args) throws Exception {        System.out.println("before calling " + method);        if (args != null) {            for (Object arg : args) {                System.out.println(arg);            }        }        Object o = method.invoke(this.proxy, args);        System.out.println("after calling " + method);        return o;    }}

MyUtils类

封装了Proxy.newProxyInstance()方法, 方便取得代理对象.

import java.lang.reflect.Proxy;public class MyUtils {    public static Object getProxy(Object obj) {        Class cls = obj.getClass();        return Proxy.newProxyInstance(                cls.getClassLoader(),                cls.getInterfaces(),                new ArrayListProxy(obj)        );    }}　　

Main

在这里进行运行测试

import java.util.ArrayList;import java.util.List;@SuppressWarnings("unchecked")public class Main {    public static void main(String[] args) {        List realList = new ArrayList
     
      (10);        List proxyList = (List) MyUtils.getProxy(realList);        proxyList.add("New");        System.out.print("\n\n");        proxyList.add("York");    }}