观察者模式

 

观察者模式(有时又被称为发布/订阅模式)是软体设计模式的一种。在此种模式中，一个目标物件管理所有相依于它的观察者物件，并且在它本身的状态改变时主动发出通知。这通常透过呼叫各观察者所提供的方法来实现。此种模式通常被用来实作事件处理系统。

 

package org.fanzone.pattern.observer;

 

/** 

 * Title: base<br> 

 * Description: Observer Criterion<br> 

 * Copyright: Copyright (c) 2011 <br> 

 * Create DateTime: Jul 4, 2011 10:16:05 AM <br> 

 * @author wangmeng

 */

public interface IObserver {

 

void receive(String message);

}

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package org.mars.pattern.observer;

/** 

 * Title: base<br> 

 * Description: Observer<br> 

 * Copyright: Copyright (c) 2011 <br> 

 * Create DateTime: Jul 4, 2011 10:17:47 AM <br> 

 * @author wangmeng

 */

public class Observer implements IObserver{

public void receive(String message) {

System.out.println(this.hashCode()+": I'v got it.");

}

}

-------------------------------------------------------------------------------

package org.mars.pattern.observer;

import java.util.ArrayList;

import java.util.List;

/** 

 * Title: base<br> 

 * Description: Subject<br> 

 * Copyright: Copyright (c) 2011 <br> 

 * Create DateTime: Jul 4, 2011 10:19:17 AM <br> 

 * @author wangmeng

 */

public class Subject {

private List<Object> observers;

/**

* Initial the container filled with observers. 

*/

public Subject(){

observers = new ArrayList<Object>();

}

/**

* Register observer.

* @param observer

*/

public void register(IObserver observer){

if(!observers.contains(observer)){

observers.add(observer);

}

}

/**

* Unregister observer.

* @param observer

*/

public void unRegister(IObserver observer){

if(observers.contains(observer)){

observers.remove(observer);

}

}

/**

* Just broadcast message to every registered member.

* @param message

*/

public void notify(String message){

System.out.println(this.hashCode() + ": " + message);

for(Object object : observers){

IObserver observer = (IObserver)object;

observer.receive(message);

}

}

}

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package org.mars.pattern.observer;

public class Commission {

public static void main(String[] args){

Subject subject = new Subject();

Observer firstObserver = new Observer();

Observer secondObserver = new Observer();

Observer thirdObserver = new Observer();

/** Register observer. */

subject.register(firstObserver);

subject.register(secondObserver);

subject.register(thirdObserver);

/** Notify a message. */

subject.notify("Going to the music party,shall we?");

/**Unregister one observer. */

subject.unRegister(thirdObserver);

/** Notify a message again. */

subject.notify("At tweenty thirty,okay?");

}

}