目的

集中相关对象之间复杂的沟通和控制方式。

类图

  • Mediator: 中介者，定义一个接口用于与各同事（Colleague）对象通信。
  • Colleague: 同事，相关对象

中介者类图.png

实现

Alarm（闹钟）、CoffeePot（咖啡壶）、Calendar（日历）、Sprinkler（喷头）是一组相关的对象，在某个对象的事件产生时需要去操作其他对象，形成了下面这种依赖结构：
中介者1.jpg
使用中介者模式可以将复杂的依赖结构变成星形结构。
中介者2.jpg

  1. public abstract class Colleague {
  2.     public abstract void onEvent(Mediator mediator);
  3. }
  6. public class Alarm extends Colleague {
  8.     @Override
  9.     public void onEvent(Mediator mediator) {
  10.         mediator.doEvent("alarm");
  11.     }
  13.     public void doAlarm() {
  14.         System.out.println("doAlarm()");
  15.     }
  16. }
  19. public class CoffeePot extends Colleague {
  20.     @Override
  21.     public void onEvent(Mediator mediator) {
  22.         mediator.doEvent("coffeePot");
  23.     }
  25.     public void doCoffeePot() {
  26.         System.out.println("doCoffeePot()");
  27.     }
  28. }
  31. public class Calender extends Colleague {
  32.     @Override
  33.     public void onEvent(Mediator mediator) {
  34.         mediator.doEvent("calender");
  35.     }
  37.     public void doCalender() {
  38.         System.out.println("doCalender()");
  39.     }
  40. }
  43. public class Sprinkler extends Colleague {
  44.     @Override
  45.     public void onEvent(Mediator mediator) {
  46.         mediator.doEvent("sprinkler");
  47.     }
  49.     public void doSprinkler() {
  50.         System.out.println("doSprinkler()");
  51.     }
  52. }
  55. public abstract class Mediator {
  56.     public abstract void doEvent(String eventType);
  57. }
  60. public class ConcreteMediator extends Mediator {
  61.     private Alarm alarm;
  62.     private CoffeePot coffeePot;
  63.     private Calender calender;
  64.     private Sprinkler sprinkler;
  66.     public ConcreteMediator(Alarm alarm, CoffeePot coffeePot, Calender calender, Sprinkler sprinkler) {
  67.         this.alarm = alarm;
  68.         this.coffeePot = coffeePot;
  69.         this.calender = calender;
  70.         this.sprinkler = sprinkler;
  71.     }
  73.     @Override
  74.     public void doEvent(String eventType) {
  75.         switch (eventType) {
  76.             case "alarm":
  77.                 doAlarmEvent();
  78.                 break;
  79.             case "coffeePot":
  80.                 doCoffeePotEvent();
  81.                 break;
  82.             case "calender":
  83.                 doCalenderEvent();
  84.                 break;
  85.             default:
  86.                 doSprinklerEvent();
  87.         }
  88.     }
  90.     public void doAlarmEvent() {
  91.         alarm.doAlarm();
  92.         coffeePot.doCoffeePot();
  93.         calender.doCalender();
  94.         sprinkler.doSprinkler();
  95.     }
  97.     public void doCoffeePotEvent() {
  98.         // ...
  99.     }
  101.     public void doCalenderEvent() {
  102.         // ...
  103.     }
  105.     public void doSprinklerEvent() {
  106.         // ...
  107.     }
  108. }
  111. public class Client {
  112.     public static void main(String[] args) {
  113.         Alarm alarm = new Alarm();
  114.         CoffeePot coffeePot = new CoffeePot();
  115.         Calender calender = new Calender();
  116.         Sprinkler sprinkler = new Sprinkler();
  117.         Mediator mediator = new ConcreteMediator(alarm, coffeePot, calender, sprinkler);
  118.         // 闹钟事件到达，调用中介者就可以操作相关对象
  119.         alarm.onEvent(mediator);
  120.     }
  121. }
  124. 运行结果
  125. doAlarm()
  126. doCoffeePot()
  127. doCalender()
  128. doSprinkler()

JDK中的体现