设计模式——中介者模式

什么是中介者模式

中介者模式是一种行为模式，其中最重要的角色就是中介者了，中介者的作用就是封装一系列对象的交互逻辑。比如在一个智能家居系统中有许多设备比如TV，屏幕，摄像头，报警器等等的启动，一般来说系统的启动需要这些设备的相互协调交互，如果这些全部暴露给Client，那么整体逻辑就会变得非常的复杂，先如今通过中介者来包装系统中的一些列对象的交互逻辑。

中介者模式UML图

Mediator是中介者，它用来封装一系列的Colleague对象之间的相互调用。即它需要知道所有的具体的同事类，即以一个集合来管理并接受某个同事对象消息，完成相应的任务。

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

代码实现

public abstract class Colleague {
  // 每个同事类中都含有对应的中介者
  private Mediator mediator;
  // 同事对象的名字
  public String name;
  // 构造的时候讲中介者和名字传入初始化
  public Colleague(Mediator mediator, String name) {
   this.mediator = mediator;
   this.name = name;
  }
  // 获取中介者，因为它需要向中介者发送消息
  public Mediator GetMediator() {
      return this.mediator;
  }
  // 发送消息
  public abstract void SendMessage(int stateChange);

}


public class Alarm extends Colleague {
  public Alarm(Mediator mediator, String name) {
    super(mediator, name);
    mediator.Register(name, this);
  }
  public void SendAlarm(int stateChange) {
    SendMessage(stateChange);
  }

  @Override
  public void SendMessage(int stateChange) {
    this.GetMediator().GetMessage(stateChange, this.name);
  }
}

public class Curtains extends Colleague {
  
  public Curtains(Mediator mediator, String name) {
    super(mediator, name);
    mediator.Register(name, this);
  }

  @Override
  public void SendMessage(int stateChange) {
    this.GetMediator().GetMessage(stateChange, this.name);
  }
  
  public void UpCurtains() {
    System.out.println("I am holding Up Curtains!");
  }
}

public class CoffeeMachine extends Colleague {
  public CoffeeMachine(Mediator mediator, String name{
    super(mediator, name);
    mediator.Register(name, this);
  }

  @Override
  public void SendMessage(int stateChange) {
    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 class TV extends Colleague {
  public TV(Mediator mediator, String name) {
    super(mediator, name);
    mediator.Register(name, this);
  }

  @Override
  public void SendMessage(int stateChange) {
    this.GetMediator().GetMessage(stateChange, this.name);
  }

  public void StartTv() {
    System.out.println("It's time to StartTv!");
  }

  public void StopTv() {
    System.out.println("StopTv!");
    }
}

public abstract class Mediator {
  
  // 将同事注册到中介者对象中
  public abstract void Register(String colleagueName, Colleague colleague);
  
  // 获取同事发送的消息
  public abstract void GetMessage(int stateChange, String colleagueName);
  
  // 发送消息
  public abstract void SendMessage();

}

public class ConcreteMediator extends Mediator {
  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) {
    colleagueMap.put(colleagueName, colleague);
    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);
    }
  }

  // 中介者协调各个同事之间的工作
  @Override
  public void GetMessage(int stateChange, String colleagueName) {
    // 如果我接受到的是Alarm那么。。。
    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();
      }
      // 如果是咖啡，那么、、、
    } else if (colleagueMap.get(colleagueName) instanceof CoffeeMachine) {
      ((Curtains) (colleagueMap.get(interMap.get("Curtains"))))
      .UpCurtains();
    } else if (colleagueMap.get(colleagueName) instanceof TV) {

    } else if (colleagueMap.get(colleagueName) instanceof Curtains) {

    }
  }
  
  @Override
  public void SendMessage() {}

}

public class ClientTest {
  
  public static void main(String[] args) {
    Mediator mediator = new ConcreteMediator();
    Alarm alarm = new Alarm(mediator, "alarm");
    CoffeeMachine coffeeMachine = new CoffeeMachi   (mediator,"coffeeMachine");
    Curtains curtains = new Curtains(mediator, "curtains");
    TV tV = new TV(mediator, "TV");
    alarm.SendAlarm(0);
    coffeeMachine.FinishCoffee();
    alarm.SendAlarm(1);
  }

}