观察者设计模式

1.定义一个抽象Observe观察者

public interface Observe {
    void update(Message message);
}

2.定义一个DBObserver观察者

public class DBObserver implements Observe {
    ObservedSubject observedSubject;
    String name;
    public DBObserver(String name,ObservedSubject observedSubject){
        this.name=name;
        this.observedSubject=observedSubject;
        observedSubject.addObserver(this);
    }
    @Override
    public void update(Message message) {
        System.out.println("数据库"+message.id+message.name+message.content);
    }
}

3.定义一个EmailObserver观察者

public class EmailObserver implements Observe {
    ObservedSubject observedSubject;
    String name;
    public EmailObserver(String name,ObservedSubject observedSubject){
        this.name=name;
        this.observedSubject=observedSubject;
        observedSubject.addObserver(this);
    }
    @Override
    public void update(Message message) {
        System.out.println("邮件"+message.id+message.name+message.content);
    }
}

4.定义一个AdminObserver观察者

public class AdminObserver implements Observe {
    ObservedSubject observedSubject;
    String name;
    public AdminObserver(String name,ObservedSubject observedSubject){
        this.name=name;
        this.observedSubject=observedSubject;
        observedSubject.addObserver(this);
    }
    @Override
    public void update(Message message) {
        System.out.println("管理员！"+message.id+message.name+message.content);
    }
}

5.定义一个ObservedSubject被观察者

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

public class ObservedSubject {
    List<Observe> observers;
    private Message message;
    public ObservedSubject(){
        observers=new ArrayList<>();
    }
    public void addObserver(Observe observe){
        observers.add(observe);
    }
    public void removeObserver(Observe observe){
        observers.remove(observe);
    }
    public void notifyObserver(){
        for (Observe observer : observers) {
            observer.update(message);
        }
    }
    public void setMessage(Message message){
        this.message=message;
        this.notifyObserver();
    }
}

6.消息Message类

public class Message {
    int id;
    String name;
    String email;
    String content;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public Message(int id, String name, String email, String content) {
        this.id = id;
        this.name = name;
        this.email = email;
        this.content = content;
    }
}

7.测试

public class Main {

    public static void main(String[] args) {
        ObservedSubject observedSubject = new ObservedSubject();
        DBObserver mysql = new DBObserver("mysql",observedSubject);
        EmailObserver qq = new EmailObserver("qq",observedSubject);
        AdminObserver usr = new AdminObserver("usr", observedSubject);
        Message message = new Message(1, "hong", "12@qq.com", "加油");
        observedSubject.setMessage(message);
    }
}

8.运行结果