Java设计模式之中介者模式

shaoshaossm

发布于 2022-12-27 14:45:58

2180

发布于 2022-12-27 14:45:58

文章被收录于专栏：Java啊

基本介绍

中介者模式（Mediator Pattern），用一个中介对象来封装一系列的对象交互。中介者使各个对象不需要显式地相互引用，从而使其耦合松散，而且可以独立地改变它们之间的交互
中介者模式属于行为型模式，使代码易于维护
比如MVC模式，C（Controller控制器）是M（Model模型）和V（View视图）的中介者，在前后端交互时起到了中间人的作用

Mediator就是抽象中介者，定义了同事对象到中介者对象的接口
Colleague是抽象同事类
Concretemediator具体的中介者对象，实现抽象方法，他需要知道所有的具体的同事类，即以一个集合来管理Hashmap，并接受某个同事对象消息，完成相应的任务
ConcreteColleague具体的同事类，会有很多，每个同事只知道自己的行为，而不了解其他同事类的行为（方法）,但是他们都依赖中介者对象

智能家庭项目：

智能家庭包括各种设备，闹钟、咖啡机、电视机、窗帘等
主人要看电视时，各个设备可以协同工作，自动完成看电视的准备工作，比如流程为：闹铃响起->咖啡机开始做咖啡->窗帘自动落下->电视机开始播放

public abstract class Mediator {
    //将给中介者对象，加入到集合中
    public abstract void Register(String colleagueName, Colleague colleague);

    //接收消息, 具体的同事对象发出
    public abstract void GetMessage(int stateChange, String colleagueName);

    public abstract void SendMessage();
}

//具体的中介者类
public class ConcreteMediator extends Mediator {
    //集合，放入所有的同事对象
    private HashMap<String, Colleague> colleagueMap;
    private HashMap<String, String> interMap;

    public ConcreteMediator() {
        colleagueMap = new HashMap<String, Colleague>();
        interMap = new HashMap<String, String>();
    }

    @Override
    public void Register(String colleagueName, Colleague colleague) {
        colleagueMap.put(colleagueName, colleague);


        if (colleague instanceof Alarm) {
            interMap.put("Alarm", colleagueName);
        } else if (colleague instanceof CoffeeMachine) {
            interMap.put("CoffeeMachine", colleagueName);
        } else if (colleague instanceof TV) {
            interMap.put("TV", colleagueName);
        } else if (colleague instanceof Curtains) {
            interMap.put("Curtains", colleagueName);
        }

    }

    //具体中介者的核心方法
    //1. 根据得到消息，完成对应任务
    //2. 中介者在这个方法，协调各个具体的同事对象，完成任务
    @Override
    public void GetMessage(int stateChange, String colleagueName) {

        //处理闹钟发出的消息
        if (colleagueMap.get(colleagueName) instanceof Alarm) {
            if (stateChange == 0) {
                ((CoffeeMachine) (colleagueMap.get(interMap
                        .get("CoffeeMachine")))).StartCoffee();
                ((TV) (colleagueMap.get(interMap.get("TV")))).StartTv();
            } else if (stateChange == 1) {
                ((TV) (colleagueMap.get(interMap.get("TV")))).StopTv();
            }

        } else if (colleagueMap.get(colleagueName) instanceof CoffeeMachine) {
            ((Curtains) (colleagueMap.get(interMap.get("Curtains"))))
                    .UpCurtains();

        } else if (colleagueMap.get(colleagueName) instanceof TV) {//如果TV发现消息

        } else if (colleagueMap.get(colleagueName) instanceof Curtains) {
            //如果是以窗帘发出的消息，这里处理...
        }

    }

    @Override
    public void SendMessage() {

    }

}

public abstract class Colleague {
    private Mediator mediator;
    public String name;

    public Colleague(Mediator mediator, String name) {

        this.mediator = mediator;
        this.name = name;

    }

    public Mediator GetMediator() {
        return this.mediator;
    }

    public abstract void SendMessage(int stateChange);
}

//具体的同事类
public class Alarm extends Colleague {

    //构造器
    public Alarm(Mediator mediator, String name) {
        super(mediator, name);
        //在创建Alarm 同事对象时，将自己放入到ConcreteMediator 对象中[集合]
        mediator.Register(name, this);
    }

    public void SendAlarm(int stateChange) {
        SendMessage(stateChange);
    }

    @Override
    public void SendMessage(int stateChange) {
        //调用的中介者对象的getMessage
        this.GetMediator().GetMessage(stateChange, this.name);
    }

}

public class CoffeeMachine extends Colleague {

    public CoffeeMachine(Mediator mediator, String name) {
        super(mediator, name);
        mediator.Register(name, this);
    }

    @Override
    public void SendMessage(int stateChange) {
        this.GetMediator().GetMessage(stateChange, this.name);
    }

    public void StartCoffee() {
        System.out.println("It's time to startcoffee!");
    }

    public void FinishCoffee() {

        System.out.println("After 5 minutes!");
        System.out.println("Coffee is ok!");
        SendMessage(0);
    }
}

public class Curtains extends Colleague {

    public Curtains(Mediator mediator, String name) {
        super(mediator, name);
        mediator.Register(name, this);
    }

    @Override
    public void SendMessage(int stateChange) {
        this.GetMediator().GetMessage(stateChange, this.name);
    }

    public void UpCurtains() {
        System.out.println("I am holding Up Curtains!");
    }

}

public class TV extends Colleague {

    public TV(Mediator mediator, String name) {
        super(mediator, name);
        mediator.Register(name, this);
    }

    @Override
    public void SendMessage(int stateChange) {
        this.GetMediator().GetMessage(stateChange, this.name);
    }

    public void StartTv() {
        System.out.println("It's time to StartTv!");
    }

    public void StopTv() {
        System.out.println("StopTv!");
    }
}

public class ClientTest {

    public static void main(String[] args) {
        //创建一个中介者对象
        Mediator mediator = new ConcreteMediator();

        //创建Alarm 并且加入到  ConcreteMediator 对象的HashMap
        Alarm alarm = new Alarm(mediator, "alarm");

        //创建了CoffeeMachine 对象，并  且加入到  ConcreteMediator 对象的HashMap
        CoffeeMachine coffeeMachine = new CoffeeMachine(mediator,
                "coffeeMachine");

        //创建 Curtains , 并  且加入到  ConcreteMediator 对象的HashMap
        Curtains curtains = new Curtains(mediator, "curtains");
        TV tV = new TV(mediator, "TV");

        //让闹钟发出消息
        alarm.SendAlarm(0);
        coffeeMachine.FinishCoffee();
        alarm.SendAlarm(1);
    }

}