设计模式之代理模式
代理模式定义：为其他对象提供一种代理以控制对这个对象的访问。
优点：
1、职责清晰。
2、高扩展性。
3、智能化。
下面分析三种形式的代理。
第一种、简单的代理模式
类图如下：
实现代码如下：
玩家抽象类：
package com.designpatterns.proxy;
public interface IGamePlayer {
public void login(String name,String password);
public void killBoss();
public void upgrade();
}
玩家实现类：
package com.designpatterns.proxy;
public class GamePlayer implements IGamePlayer {
private String name="";
public GamePlayer(String name) {
this.name=name;
}
@Override
public void login(String name, String password) {
System.out.println("用户名为："+name+"的用户,"+this.name+"登录了！");
}
@Override
public void killBoss() {
System.out.println(this.name+"正在打怪！");
}
@Override
public void upgrade() {
System.out.println(this.name+"升一级！");
}
}
代理实现类：
package com.designpatterns.proxy;
public class GamePlayerProxy implements IGamePlayer {
private IGamePlayer gamePlayer=null;
public GamePlayerProxy(IGamePlayer gamePlayer) {
this.gamePlayer=gamePlayer;
}
@Override
public void login(String name, String password) {
this.gamePlayer.login(name, password);
}
@Override
public void killBoss() {
this.gamePlayer.killBoss();
}
@Override
public void upgrade() {
this.gamePlayer.upgrade();
}
}
测试类：
package com.designpatterns.proxy;
public class Client {
public static void main(String[] args) {
IGamePlayer zs = new GamePlayer("张三");
IGamePlayer proxy = new GamePlayerProxy(zs);
proxy.login("zhangsan", "123456");
proxy.killBoss();
proxy.upgrade();
}
}
第二种：
强制代理
这种情况下，必须通过制定的代理，才能访问到处理事件。
类图如下：
实现代码如下：
玩家抽象类;
package com.designpatterns.proxyforced;
public interface IGamePlayer {
public void login(String name,String password);
public void killBoss();
public void upgrade();
public IGamePlayer getProxy();
}
玩家实现类：
package com.designpatterns.proxyforced;
public class GamePlayer implements IGamePlayer {
private String name="";
private IGamePlayer proxy;
public GamePlayer(String name) {
this.name=name;
}
@Override
public void login(String name, String password) {
if (this.isProxy()) {
System.out.println("用户名为："+name+"的用户,"+this.name+"登录了！");
}else {
System.out.println("请使用制定的代理！");
}
}
@Override
public void killBoss() {
if (this.isProxy()) {
System.out.println(this.name+"正在打怪！");
}else {
System.out.println("请使用制定的代理！");
}
}
@Override
public void upgrade() {
if (this.isProxy()) {
System.out.println(this.name+"升一级！");
}else {
System.out.println("请使用制定的代理！");
}
}
@Override
public IGamePlayer getProxy() {
if(this.proxy==null){
this.proxy=new GamePlayerProxy(this);
}
return this.proxy;
}
private boolean isProxy(){
if(this.proxy==null){
return false;
}else {
return true;
}
}
}
代理实现类：
package com.designpatterns.proxyforced;
public class GamePlayerProxy implements IGamePlayer {
private IGamePlayer gamePlayer=null;
public GamePlayerProxy(IGamePlayer gamePlayer) {
this.gamePlayer=gamePlayer;
}
@Override
public void login(String name, String password) {
this.gamePlayer.login(name, password);
}
@Override
public void killBoss() {
this.gamePlayer.killBoss();
}
@Override
public void upgrade() {
this.gamePlayer.upgrade();
}
@Override
public IGamePlayer getProxy() {
return this;
}
}
测试类：
package com.designpatterns.proxyforced;
public class Client {
public static void main(String[] args) {
IGamePlayer zs = new GamePlayer("张三");
System.out.println("-----------------------------\n错误的用法");
IGamePlayer proxy = new GamePlayerProxy(zs);
proxy.login("zhangsan", "123456");
proxy.killBoss();
proxy.upgrade();
System.out.println("-----------------------------\n正确的用法");
proxy = zs.getProxy();
proxy.login("zhangsan", "123456");
proxy.killBoss();
proxy.upgrade();
}
}
第三种、 动态代理
动态代理是在实现阶段不用关心代理谁，而在运行阶段才指定代理哪一个对象。（AOP就是典型的例子）
类图如下：
代码实现如下：
抽象的代理对象：
package com.designpatterns.dynamicproxy;
public interface Subject {
public void sayHello();
public void sayByeBye();
}
实现的代理对象;
package com.designpatterns.dynamicproxy;
public class RealSubject implements Subject {
@Override
public void sayHello() {
System.out.println("hello!");
}
@Override
public void sayByeBye() {
System.out.println("ByeBye!");
}
}
动态代理的Handler类：
package com.designpatterns.dynamicproxy;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
public class MyInvocationHandler implements InvocationHandler {
private Object target = null;
public MyInvocationHandler(Object object) {
this.target = object;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
(new Before()).sayBefore();//AOP
Object o = method.invoke(this.target, args);
(new After()).sayAfter();//AOP
return o;
}
}
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在这里打断一下，为了体现AOP的编程思想，我们可以在这里实现一个简单的切面编程，我定义了两个方法。然后在动态代理的Handler类中调用。
After类：
package com.designpatterns.dynamicproxy;
public class After {
public void sayAfter() {
System.out.println("I am after!");
}
}
Before类：
package com.designpatterns.dynamicproxy;
public class Before {
public void sayBefore() {
System.out.println("I am before!");
}
}
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动态代理类：
package com.designpatterns.dynamicproxy;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
public class SubjectDynamicProxy<T> {
@SuppressWarnings("unchecked")
public static <T> T newProxyInstance(Object O) {
ClassLoader loader = O.getClass().getClassLoader();
Class<?>[] interfaces = O.getClass().getInterfaces();
InvocationHandler h = new MyInvocationHandler(O);
return (T) Proxy.newProxyInstance(loader, interfaces, h);
}
}
测试类：
package com.designpatterns.dynamicproxy;
public class Client {
public static void main(String[] args) {
RealSubject realSubject= new RealSubject();
Subject subjectProxy= SubjectDynamicProxy.newProxyInstance(realSubject);
subjectProxy.sayHello();
subjectProxy.sayByeBye();
}
}
以上就是三种形式的代理模式。
参考资料：
设计模式之禅
备注：
转载请注明出处
http://blog.csdn.net/wsyw126/article/details/51313972
by WSYW126