利用JDK方式和GuavaAPI方式实现观察者模式

1、JDK方法实现案例需求：

去餐厅吃饭有时候需要排队，进行排队叫号。假如所有等待的人都是观察者，叫号系统就是一个被监听的主题对象。当叫号系统发出叫号通知后，所有等待的人，都会收到通知，然后检查自己的号码是否匹配。匹配的话，就开始就餐，不匹配的，继续等待

package com.gupao.jay.pattern.observer.jdk;

/**
 * @Author JAY
 * @Date 2019/6/2 8:41
 * @Description 排队的号码
 **/
public class NumberModel {

    private int number;
    private String deskType;

    public NumberModel(int number, String deskType) {
        this.number = number;
        this.deskType = deskType;
    }

    public int getNumber() {
        return number;
    }

    public void setNumber(int number) {
        this.number = number;
    }

    public String getDeskType() {
        return deskType;
    }

    public void setDeskType(String deskType) {
        this.deskType = deskType;
    }

    @Override
    public String toString() {
        return "NumberModel{" +
                "number=" + number +
                ", deskType=‘" + deskType + ‘\‘‘ +
                ‘}‘;
    }
}

 1 package com.gupao.jay.pattern.observer.jdk;
 2
 3 import java.util.Observable;
 4 import java.util.Observer;
 5
 6 /**
 7  * @Author JAY
 8  * @Date 2019/6/2 8:40
 9  * @Description 等待的顾客
10  **/
11 public class Consumer implements Observer {
12
13     public Consumer(int number) {
14         this.number = number;
15     }
16
17     private int number;
18
19     public int getNumber() {
20         return number;
21     }
22
23     public void setNumber(int number) {
24         this.number = number;
25     }
26
27     @Override
28     public void update(Observable o, Object arg) {
29         NumberModel numberModel = (NumberModel) arg;
30         if (numberModel.getNumber() != this.number){
31             System.out.println("号码不匹配，继续等待。。。。");
32             return;
33         }
34         System.out.println("排到我们了，前往" + numberModel.getDeskType() + "用餐");
35     }
36 }

package com.gupao.jay.pattern.observer.jdk;

import java.util.Observable;
import java.util.Observer;
import java.util.concurrent.locks.Lock;

/**
 * @Author JAY
 * @Date 2019/6/2 8:42
 * @Description 叫号系统
 **/
public class CallNumberSystem extends Observable {

    private CallNumberSystem(){}

    private static CallNumberSystem callNumberSystem = null;

    public static CallNumberSystem getInstance(){
        if (callNumberSystem == null){
            synchronized (CallNumberSystem.class){
                if (callNumberSystem == null){
                    callNumberSystem = new CallNumberSystem();
                }
            }
        }
        return callNumberSystem;
    }

    public void notifyNumber(NumberModel numberModel){
        System.out.println("系统播报：请" + numberModel.getNumber() + "号顾客到" + numberModel.getDeskType() + "就餐！");
        setChanged();
        notifyObservers(numberModel);
    }
}

package com.gupao.jay.pattern.observer.jdk;

/**
 * @Author JAY
 * @Date 2019/6/2 8:55
 * @Description TODO
 **/
public class CallNumberSystemTest {

    public static void main(String[] args) {
        Consumer consumerA = new Consumer(10001);
        Consumer consumerB = new Consumer(10002);
        Consumer consumerC = new Consumer(10003);

        CallNumberSystem instance = CallNumberSystem.getInstance();
        instance.addObserver(consumerA);
        instance.addObserver(consumerB);
        instance.addObserver(consumerC);

        instance.notifyNumber(new NumberModel(10002,"小桌A11号"));

    }

}

2、guavaAPI实现案例需求：模拟在社区中，学生向老师提问。

 1 package com.gupao.jay.pattern.observer.guava;
 2
 3 /**
 4  * @Author JAY
 5  * @Date 2019/6/2 9:11
 6  * @Description 问题
 7  **/
 8 public class Question {
 9
10     private String userName;
11     private String content;
12
13     public String getUserName() {
14         return userName;
15     }
16
17     public void setUserName(String userName) {
18         this.userName = userName;
19     }
20
21     public String getContent() {
22         return content;
23     }
24
25     public void setContent(String content) {
26         this.content = content;
27     }
28 }

package com.gupao.jay.pattern.observer.guava;

import com.google.common.eventbus.Subscribe;

/**
 * @Author JAY
 * @Date 2019/6/2 9:05
 * @Description TODO
 **/
public class Teacher {

    private String name;

    public Teacher(String name) {
        this.name = name;
    }

    @Subscribe
    public void subscribe(Question question){
    //业务逻辑
        System.out.println(this.name + "老师，学生" + question.getUserName() + "向你提了一个问题，问题的内容是:" + question.getContent());
    }
}

 1 package com.gupao.jay.pattern.observer.guava;
 2
 3 import com.google.common.eventbus.EventBus;
 4
 5 /**
 6  * @Author JAY
 7  * @Date 2019/6/2 9:11
 8  * @Description TODO
 9  **/
10 public class GuavaTest {
11     public static void main(String[] args) {
12         Question question = new Question();
13         question.setUserName("JayNing");
14         question.setContent("如何阅读spring源码？");
15
16         Teacher tom = new Teacher("Tom");
17         Teacher mic = new Teacher("Mic");
18
19         EventBus eventBus = new EventBus();
20         eventBus.register(tom);
21         eventBus.register(mic);
22         eventBus.post(question);
23     }
24 }

原文地址：https://www.cnblogs.com/ningJJ/p/10962303.html