设计模式18-中介者模式

1. 概念

    用一个中介对象封装一些列的对象交互

2. 案例

    实现下面的案例

    类A和B，类中各有一个数字，要保证类B中的数字永远是类A中数字的100倍。即：当修改类A的数时，将这个数字乘以100赋给类B，而修改类B时，要将数除以100赋给类A。类A类B互相影响，

就称为同事类 . 

    如果不使用中介者模式的代码如下： 

abstract class AbstractColleague {  
    protected int number;  
  
    public int getNumber() {  
        return number;  
    }  
  
    public void setNumber(int number){  
        this.number = number;  
    }  
    //抽象方法，修改数字时同时修改关联对象  
    public abstract void setNumber(int number, AbstractColleague coll);  
}  
  
class ColleagueA extends AbstractColleague{  
    public void setNumber(int number, AbstractColleague coll) {  
        this.number = number;  
        coll.setNumber(number*100);  
    }  
}  
  
class ColleagueB extends AbstractColleague{  
      
    public void setNumber(int number, AbstractColleague coll) {  
        this.number = number;  
        coll.setNumber(number/100);  
    }  
}  
  
public class Client {  
    public static void main(String[] args){  
  
        AbstractColleague collA = new ColleagueA();  
        AbstractColleague collB = new ColleagueB();  
          
        System.out.println("==========设置A影响B==========");  
        collA.setNumber(1288, collB);  
        System.out.println("collA的number值："+collA.getNumber());  
        System.out.println("collB的number值："+collB.getNumber());  
  
        System.out.println("==========设置B影响A==========");  
        collB.setNumber(87635, collA);  
        System.out.println("collB的number值："+collB.getNumber());  
        System.out.println("collA的number值："+collA.getNumber());  
    }  
}  

下面看中介者模式的实现： 

 类A类B通过直接的关联发生关系，假如我们要使用中介者模式，类A类B之间则不可以直接关联，他们之间必须要通过一个中介者来达到关联的目的

abstract class AbstractColleague {  
    protected int number;  
  
    public int getNumber() {  
        return number;  
    }  
  
    public void setNumber(int number){  
        this.number = number;  
    }  
    //注意这里的参数不再是同事类，而是一个中介者  
    public abstract void setNumber(int number, AbstractMediator am);  
}  
  
class ColleagueA extends AbstractColleague{  
  
    public void setNumber(int number, AbstractMediator am) {  
        this.number = number;  
        am.AaffectB();  
    }  
}  
  
class ColleagueB extends AbstractColleague{  
  
    @Override  
    public void setNumber(int number, AbstractMediator am) {  
        this.number = number;  
        am.BaffectA();  
    }  
}  
  
abstract class AbstractMediator {  
    protected AbstractColleague A;  
    protected AbstractColleague B;  
      
    public AbstractMediator(AbstractColleague a, AbstractColleague b) {  
        A = a;  
        B = b;  
    }  
  
    public abstract void AaffectB();  
      
    public abstract void BaffectA();  
  
}  
class Mediator extends AbstractMediator {  
  
    public Mediator(AbstractColleague a, AbstractColleague b) {  
        super(a, b);  
    }  
  
    //处理A对B的影响  
    public void AaffectB() {  
        int number = A.getNumber();  
        B.setNumber(number*100);  
    }  
  
    //处理B对A的影响  
    public void BaffectA() {  
        int number = B.getNumber();  
        A.setNumber(number/100);  
    }  
}  
  
public class Client {  
    public static void main(String[] args){  
        AbstractColleague collA = new ColleagueA();  
        AbstractColleague collB = new ColleagueB();  
          
        AbstractMediator am = new Mediator(collA, collB);  
          
        System.out.println("==========通过设置A影响B==========");  
        collA.setNumber(1000, am);  
        System.out.println("collA的number值为："+collA.getNumber());  
        System.out.println("collB的number值为A的10倍："+collB.getNumber());  
  
        System.out.println("==========通过设置B影响A==========");  
        collB.setNumber(1000, am);  
        System.out.println("collB的number值为："+collB.getNumber());  
        System.out.println("collA的number值为B的0.1倍："+collA.getNumber());  
          
    }  
}