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设计模式-中介者模式

1.问题引出

1. 当各电器对象有多种状态改变时，相互之间的调用关系会比较复杂
2. 各个电器对象彼此联系， 你中有我，我中有你，不利于松耦合.
3. 各个电器对象之间所传递的消息(参数)，容易混乱
4. 当系统增加一个新的电器对象时，或者执行流程改变时，代码的可维护性、扩展性都不理想 ->考虑中介者模式

4.中介者模式

1. 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
2. 中介者模式属于行为型模式，使代码易于维护
3. 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

原理类图

5.使用中介者模式解决问题

package com.atguigu.mediator.smarthouse;//同事抽象类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);}

package com.atguigu.mediator.smarthouse;//具体的同事类public class Alarm extends Colleague {
   	//构造器	public Alarm(Mediator mediator, String name) {
   		super(mediator, name);		// TODO Auto-generated constructor stub		//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) {
   		// TODO Auto-generated method stub		//调用的中介者对象的getMessage		this.GetMediator().GetMessage(stateChange, this.name);	}}

package com.atguigu.mediator.smarthouse;public class CoffeeMachine extends Colleague {
   	public CoffeeMachine(Mediator mediator, String name) {
   		super(mediator, name);		// TODO Auto-generated constructor stub		mediator.Register(name, this);	}	@Override	public void SendMessage(int stateChange) {
   		// TODO Auto-generated method stub		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);	}}

package com.atguigu.mediator.smarthouse;public class Curtains extends Colleague {
   	public Curtains(Mediator mediator, String name) {
   		super(mediator, name);		// TODO Auto-generated constructor stub		mediator.Register(name, this);	}	@Override	public void SendMessage(int stateChange) {
   		// TODO Auto-generated method stub		this.GetMediator().GetMessage(stateChange, this.name);	}	public void UpCurtains() {
   		System.out.println("I am holding Up Curtains!");	}}

package com.atguigu.mediator.smarthouse;public class TV extends Colleague {
   	public TV(Mediator mediator, String name) {
   		super(mediator, name);		// TODO Auto-generated constructor stub		mediator.Register(name, this);	}	@Override	public void SendMessage(int stateChange) {
   		// TODO Auto-generated method stub		this.GetMediator().GetMessage(stateChange, this.name);	}	public void StartTv() {
   		// TODO Auto-generated method stub		System.out.println("It's time to StartTv!");	}	public void StopTv() {
   		// TODO Auto-generated method stub		System.out.println("StopTv!");	}}

package com.atguigu.mediator.smarthouse;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();}

package com.atguigu.mediator.smarthouse;import java.util.HashMap;//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
   
     colleagueMap;	private HashMap
    
      interMap;	public ConcreteMediator() {
   		colleagueMap = new HashMap
     
      ();		interMap = new HashMap
      
       ();	}	@Override	public void Register(String colleagueName, Colleague colleague) {
   		// TODO Auto-generated method stub		colleagueMap.put(colleagueName, colleague);		// TODO Auto-generated method stub		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) {
   		// TODO Auto-generated method stub		//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() {
   		// TODO Auto-generated method stub	}}
      
     
    
   

package com.atguigu.mediator.smarthouse;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);	}}

6.中介者模式的注意事项和细节

1. 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
2. 减少类间依赖，降低了耦合，符合迪米特原则
3. 中介者承担了较多的责任，一旦中介者出现了问题，整个系统就会受到影响
4. 如果设计不当，中介者对象本身变得过于复杂，这点在实际使用时，要特别注意

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