设计模式-中介者模式
1.问题引出
2.传统解决方法
3.传统方案存在的问题
- 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
- 各个电器对象彼此联系， 你中有我，我中有你，不利于松耦合.
- 各个电器对象之间所传递的消息(参数)，容易混乱
- 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
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
原理类图
对原理类图的说明- - 即(中介者模式的角色及职责)
5.使用中介者模式解决问题
代码实现
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<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
}
}
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
- 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 - 减少类间依赖，降低了耦合，符合迪米特原则
- 中介者承担了较多的责任，一旦中介者出现了问题，整个系统就会受到影响
- 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
