8000 观察者模式 · Folgerjun/DesignPatterns-Java@4fa3d0f · GitHub
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观察者模式
观察者模式
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‎java-des/src/com/java/design/observer/Observer.java

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package com.java.design.observer;
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/**
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* 观察者接口
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*
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* @author Administrator
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*
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*/
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public interface Observer {
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void update(String message);
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}

‎java-des/src/com/java/design/observer/ObserverPattern.java

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package com.java.design.observer;
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/**
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* 观察者模式 -----> 在对象之间定义了一对多的依赖，这样一来，当一个对象改变状态，依赖它的对象会收到通知并自动更新。
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*
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* 其实就是发布订阅模式，发布者发布信息，订阅者获取信息，订阅了就能收到信息，没订阅就收不到信息
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*
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* @author Administrator
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*
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*/
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public class ObserverPattern {
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public static void main(String[] args) {
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ObserverServer observerServer = new ObserverServer();
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Observer observerA = new User("A");
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Observer observerB = new User("B");
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Observer observerC = new User("C");
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observerServer.add(observerA);
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observerServer.add(observerB);
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observerServer.add(observerC);
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observerServer.setInfomation("PHP是世界上最好的语言 ...");
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System.out.println("------------------------------");
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observerServer.remove(observerB);
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observerServer.setInfomation("JAVA是世界上最好的语言 ...");
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}
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}

‎java-des/src/com/java/design/observer/ObserverServer.java

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package com.java.design.observer;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* 被观察者服务
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*
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* @author Administrator
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*
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*/
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public class ObserverServer implements Observerable {
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private List<Observer> observers;
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private String message;
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public ObserverServer() {
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observers = new ArrayList<Observer>();
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}
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@Override
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public void add(Observer observer) {
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observers.add(observer);
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}
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@Override
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public void remove(Observer observer) {
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if (!observers.isEmpty()) {
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observers.remove(observer);
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}
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}
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@Override
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public void notifyObs() {
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for (int i = 0; i < observers.size(); i++) {
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Observer obs = observers.get(i);
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obs.update(message);
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}
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}
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public void setInfomation(String message) {
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this.message = message;
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System.out.println("服务更新消息：" + message);
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notifyObs();
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}
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}

‎java-des/src/com/java/design/observer/Observerable.java

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package com.java.design.observer;
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/**
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* 被观察者接 6D40 / 声明了添加、删除、通知观察者方法
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*
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* @author Administrator
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*
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*/
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public interface Observerable {
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/**
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* 添加观察者
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*
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* @param observer
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*/
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void add(Observer observer);
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/**
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* 删除观察者
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*
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* @param observer
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*/
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void remove(Observer observer);
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/**
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* 通知观察者
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*
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*/
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void notifyObs();
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}

‎java-des/src/com/java/design/observer/User.java

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package com.java.design.observer;
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public class User implements Observer {
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private String name;
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private String message;
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public User(String name) {
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this.name = name;
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}
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@Override
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public void update(String message) {
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this.message = message;
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read();
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}
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public void read() {
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System.out.println(name + "收到推送消息：" + message);
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}
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}

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