java设计模式之中介者模式-编程知识

中介者模式（Mediator Pattern）

基本介绍

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式地相互引用，从而使其解耦松散。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。
比如MVC模式，Controller控制器是Model和View视图的中介者，再前后端交互时起到了中间人的作用。

原理类图

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。
ConcreteColleague: 具体的同事类，会有很多，每个同事只知道自己行为，而不了解其他同事类的行为，但是他们都依赖中介者对象。

应用实例

智能家庭包括各种设备，闹钟，咖啡机，电视机，窗帘等。
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，比如流程是：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。

思路分析类图：

代码如下：

//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);
}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>();}@Overridepublic void Register(String colleagueName, Colleague colleague) {// TODO Auto-generated method stubcolleagueMap.put(colleagueName, colleague);// TODO Auto-generated method stubif (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@Overridepublic 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...}}@Overridepublic void SendMessage() {// TODO Auto-generated method stub}
}//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);}@Overridepublic void SendMessage(int stateChange) {// TODO Auto-generated method stub//调用的中介者对象的getMessagethis.GetMediator().GetMessage(stateChange, this.name);}
}public class CoffeeMachine extends Colleague {public CoffeeMachine(Mediator mediator, String name) {super(mediator, name);// TODO Auto-generated constructor stubmediator.Register(name, this);}@Overridepublic void SendMessage(int stateChange) {// TODO Auto-generated method stubthis.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);// TODO Auto-generated constructor stubmediator.Register(name, this);}@Overridepublic void SendMessage(int stateChange) {// TODO Auto-generated method stubthis.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);// TODO Auto-generated constructor stubmediator.Register(name, this);}@Overridepublic void SendMessage(int stateChange) {// TODO Auto-generated method stubthis.GetMediator().GetMessage(stateChange, this.name);}public void StartTv() {// TODO Auto-generated method stubSystem.out.println("It's time to StartTv!");}public void StopTv() {// TODO Auto-generated method stubSystem.out.println("StopTv!");}
}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HashMapAlarm alarm = new Alarm(mediator, "alarm");//创建了CoffeeMachine 对象，并  且加入到  ConcreteMediator 对象的HashMapCoffeeMachine coffeeMachine = new CoffeeMachine(mediator,"coffeeMachine");//创建 Curtains , 并  且加入到  ConcreteMediator 对象的HashMapCurtains 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);}