1、例子
智能家庭项目:
1) 智能家庭包括各种设备,闹钟、咖啡机、电视机、窗帘 等
2) 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
传统解决:
流程不清晰

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
中介者:
2、基本定义
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
3、代码

public class Alarm extends Colleague {
public Alarm(Mediator mediator, String name) {
super(mediator, name);
// TODO Auto-generated constructor stub
mediator.Register(name, this);
}
public void SendAlarm(int stateChange) {
SendMessage(stateChange);
}
@Override
public void SendMessage(int stateChange) {
// TODO Auto-generated method stub
this.GetMediator().GetMessage(stateChange, this.name);
}
}
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);
}
}
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 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) {
// 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
}
}
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!");
}
}
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();
}
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!");
}
}
总结:创建由下至上。底层各个获取资源的 各自为类,没有关联。调用逻辑有中介类实现