1、观察者模式，又称订阅发布模式，其架构如下：
2、实例demo——订阅天气，发布天气
1>WeatherSubject 目标类
| public class WeatherSubject {
private List<Observer> observers = new ArrayList<Observer>();
public void attach(Observer observer){ observers.add(observer); }
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public void detach(Observer observer){ observers.remove(observer); }
protected void notifyObservers(){ for(Observer observer : observers){ observer.update(this); } }
} |
2> 具体的目标类
| public class ConcreteWeatherSubject extends WeatherSubject {
private String weatherContent;
public String getWeatherContent() { return weatherContent; }
public void setWeatherContent(String weatherContent) { this.weatherContent = weatherContent; this.notifyObservers(); }
}
|
3> 观察者
| public interface Observer {
public void update(WeatherSubject subject);
}
|
4> 具体的观察者
| public class ConcreteObserver implements Observer {
private String observerName; private String weatherContent; private String remindThing;
@Override public void update(WeatherSubject subject) { weatherContent = ((ConcreteWeatherSubject)subject).getWeatherContent(); System.out.println(observerName + "收到了" + weatherContent + " ," + remindThing); }
public String getObserverName() { return observerName; }
public void setObserverName(String observerName) { this.observerName = observerName; }
public String getWeatherContent() { return weatherContent; }
public void setWeatherContent(String weatherContent) { this.weatherContent = weatherContent; }
public String getRemindThing() { return remindThing; }
public void setRemindThing(String remindThing) { this.remindThing = remindThing; }
} |
5> test 类
| public class test {
public static void main(String[] args) { //1.创建目标 ConcreteWeatherSubject weather = new ConcreteWeatherSubject();
//2.创建观察者 ConcreteObserver observerGirl = new ConcreteObserver(); observerGirl.setObserverName("girl"); observerGirl.setRemindThing("go shopping");
ConcreteObserver observerBoy = new ConcreteObserver(); observerBoy.setObserverName("boy"); observerBoy.setRemindThing("play football");
//3.注册观察者 weather.attach(observerGirl); weather.attach(observerBoy);
//4.目标发布天气 weather.setWeatherContent("a nice day!"); }
}
|
测试结果：
girl收到了a nice day! ,go shopping
boy收到了a nice day! ,play football