设计模式11---观察者模式

观察者模式实质就是提取：提取监听对象的过程是相同的，也就是说observer类为根据不同的subject的状态做出相应的反应。

package com.jayfulmath.designpattern.observer;

public abstract class Observer {

    protected String name;
    protected ISubject sub;    

    public Observer(String name, ISubject sub) {
        this.name = name;
        this.sub = sub;
    }
    public abstract void Update();
}

public interface ISubject {
    public void Attach(Observer obs);
    public void Detach(Observer obs);
    public void Broadcast();
    public String getSubjectStatus();
    public void setSubjectStatus(String subjectStatus);
}

public class NBALooker extends Observer {

public NBALooker(String name, ISubject sub) {
        super(name, sub);
        // TODO Auto-generated constructor stub
    }

@Override
    public void Update() {
        System.out.println(sub.getSubjectStatus()+"\t"+name+"\tstop NBA Look");
    }

}

public class NBALooker extends Observer {

    public NBALooker(String name, ISubject sub) {
        super(name, sub);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void Update() {
        System.out.println(sub.getSubjectStatus()+"\t"+name+"\tstop NBA Look");
    }

}

public class StockLooker extends Observer {

    public StockLooker(String name, ISubject sub) {
        super(name, sub);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void Update() {
        // TODO Auto-generated method stub
        System.out.println(sub.getSubjectStatus()+"\t"+name+"\tstop Stock Look");
    }

}

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

public class Boss implements ISubject {

    List<Observer> _mObservers = new ArrayList<Observer>();
    public String subjectStatus;

    public void Attach(Observer obs)
    {
        _mObservers.add(obs);
    }

    public void Detach(Observer obs)
    {
        _mObservers.remove(obs);
    }

    public void Broadcast()
    {
        //here may be asynchronous to notify observer
        for(Observer observer :_mObservers)
        {
            observer.Update();
        }
    }

    /**
     * @return the subjectStatus
     */
    public String getSubjectStatus() {
        return subjectStatus;
    }

    /**
     * @param subjectStatus the subjectStatus to set
     */
    public void setSubjectStatus(String subjectStatus) {
        this.subjectStatus = subjectStatus;
    }
}

main:

public class ObserverMain extends BasicExample {

    @Override
    public void startDemo() {
        ISubject huhanshang = new Boss();
        Observer maweidong = ObserverFactory.Factory("NBALooker", "maweidong", huhanshang);
        Observer zhangdashang = ObserverFactory.Factory("StockLooker", "zhangdashang", huhanshang);

        huhanshang.Attach(maweidong);
        huhanshang.Attach(zhangdashang);

        huhanshang.setSubjectStatus("I am back! Huhan Shang!");
        huhanshang.Broadcast();
    }

}