代理模式-JDK Proxy(Java實現)

代理模式-JDK Proxy

使用JDK支持的代理模式, 動態代理

場景以下: 本文例子代理了ArrayList, 在ArrayList每次操做時, 在操做以前和以後都進行一些額外的操做.

ArrayListProxy類

這裏是代理的實現.

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類

封裝了Proxy.newProxyInstance()方法, 方便取得代理對象.

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

在這裏進行運行測試

import java.util.ArrayList;
import java.util.List;

@SuppressWarnings("unchecked")
public class Main {
    public static void main(String[] args) {
        List realList = new ArrayList<String>(10);

        List proxyList = (List) MyUtils.getProxy(realList);

        proxyList.add("New");

        System.out.print("\n\n");

        proxyList.add("York");
    }
}