Proxy代理模式（一）静态代理

Proxy pattern

In computer programming, the proxy pattern is a software design pattern. A proxy, in its most general form, is a class functioning as an interface to something else. The proxy could interface to anything: a network connection, a large object in memory, a file, or some other resource that is expensive or impossible to duplicate. In short, a proxy is a wrapper or agent object that is being called by the client to access the real serving object behind the scenes. Use of the proxy can simply be forwarding to the real object, or can provide additional logic. In the proxy, extra functionality can be provided, for example caching when operations on the real object are resource intensive, or checking preconditions before operations on the real object are invoked. For the client, usage of a proxy object is similar to using the real object, because both implement the same interface. —Wikipedia

Structure

UML class and sequence diagram

Example

import java.util.Random;

/**
 *记录坦克的移动时间
 */
public class Tank implements Movable {

    /**
     * 模拟坦克移动了一段儿时间
     */
    @Override
    public void move() {
        System.out.println("Tank moving claclacla...");
        try {
            Thread.sleep(new Random().nextInt(10000));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
			 //像不像装饰器模式！！！你细品！多态的运用！
       new TankLogProxy(new TankTimeProxy(new Tank())).move();
    }
}

class TankTimeProxy implements Movable {
    Movable m;

    public TankTimeProxy(Movable m) {
        this.m = m;
    }

    @Override
    public void move() {
        long start = System.currentTimeMillis();
        m.move();
        long end = System.currentTimeMillis();
        System.out.println(end - start);
    }
}

class TankLogProxy implements Movable {
    Movable m;

    public TankLogProxy(Movable m) {
        this.m = m;
    }

    @Override
    public void move() {
        System.out.println("start moving...");
        m.move();
        long end = System.currentTimeMillis();
        System.out.println("stopped!");
    }
}

interface Movable {
    void move();
}

Summary

静态代理和装饰器模式有点像。

但是如果想让上面例子中的TankTimeProxy可以重用，可以代理其他任何可以代理的类型 Object，要怎么做呢？