中介者设计模式

中介者模式：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示地相互引用，从而使其耦合松散，而且可以独立地改变他们之间的交互

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，在前后端交互起到中间人的作用

Mediator：抽象中介者，定义了同事对象到中介者对象的接口

ConcreteMediator：具体的中介者对象，实现了抽象方法，它需要知道所有的具体的同事类，即以一个集合来管理HashMap，并接收某个同事对象消息，完成相应的任务

Collague：抽象同事类

ConcreteCollague：具体的同事类，会有很多，每个同时类只知道自己的行为，而不了解其他同事类的行为，但他们都依赖中介者对象

• 多个类相互耦合，会形成网状结构，使用中介者模式将网状结构分离为星型结构，进行解耦
• 减少类之间的依赖，降低耦合，符合迪米特原则
• 中介者承担了较多的责任，一旦中介者出现问题，整个系统都会受到影响
• 中介者本身过于复杂

​ 智能家庭设备：闹钟、咖啡机、电视机、窗帘

​ 各个设备协同工作，自动完成看电视的准备工作和后续工作：
​ 闹钟响起->启动咖啡机开始做咖啡->降下窗帘->电视机开始播放—>关闭咖啡机喝咖啡->电视机关闭->窗帘拉起

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);



}

public class Alarm extends Colleague {

    
    public Alarm(Mediator mediator, String name) {
        super(mediator, name);
        mediator.register(name, this);
    }


    
    @Override
    public void sendMessage(int stateChange) {
        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("启动咖啡机!");
    }

    
    public void finishCoffee() {
        System.out.println("5分钟后!");
        stopCoffee();
        System.out.println("喝咖啡!");
    }


    
    public void stopCoffee() {
        System.out.println("关闭咖啡机!");
    }



}

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 downCurtains() {
        System.out.println("拉下窗帘！");
    }


    
    public void upCurtains() {
        System.out.println("升起窗帘！");
    }



}

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("打开电视!");
    }

    
    public void stopTV() {
        System.out.println("关闭电视!");
    }

}

public abstract class Mediator {

    
    public abstract void register(String colleagueName, Colleague colleague);

    
    public abstract void getMessage(int stateChange, String colleagueName);


}

public class ConcreteMediator extends Mediator {

    private HashMap colleaguesMap;

    private HashMap interMap;

    public ConcreteMediator() {
        colleaguesMap = new HashMap<>();
        interMap = new HashMap<>();
    }

    
    @Override
    public void register(String colleagueName, Colleague colleague) {
        colleaguesMap.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);
        }

    }

    
    @Override
    public void getMessage(int stateChange, String colleagueName) {
        if (colleaguesMap.get(colleagueName) instanceof Alarm) {
            if (stateChange == 0) {
                ((CoffeeMachine) (colleaguesMap.get(interMap.get("CoffeeMachine")))).startCoffee();
                ((Curtains) (colleaguesMap.get(interMap.get("Curtains")))).downCurtains();
                ((TV) (colleaguesMap.get(interMap.get("TV")))).startTV();
            } else if (stateChange == 1) {
                ((TV) (colleaguesMap.get(interMap.get("TV")))).stopTV();
                ((Curtains) (colleaguesMap.get(interMap.get("Curtains")))).upCurtains();
            }
        } else if (colleaguesMap.get(colleagueName) instanceof CoffeeMachine) {
           ((CoffeeMachine) (colleaguesMap.get(interMap.get("CoffeeMachine")))).finishCoffee();
        } else if (colleaguesMap.get(colleagueName) instanceof TV) {

        } else if (colleaguesMap.get(colleagueName) instanceof Curtains) {

        }
    }
}

public class Client {

    
    public static void main(String[] args) {

        Mediator mediator = new ConcreteMediator();

        Colleague alarm = new Alarm(mediator,"闹钟");
        Colleague coffeeMachine = new CoffeeMachine(mediator,"咖啡机");
        Colleague tv = new TV(mediator,"电视机");
        Colleague curtains = new Curtains(mediator,"窗帘");

        alarm.sendMessage(0);
        coffeeMachine.sendMessage(0);
        alarm.sendMessage(1);

    }

}