设计模式学习笔记十八：中介者模式

设计模式学习笔记十八：中介者模式

介绍

中介者（MEDIATOR）模式属于对象行为型模式。主要目的是将对象间复杂的调用关系进行解耦。使所有的对象都通过这个中介者进行交互。

优点

• 对象解耦，提供了复用性；
• 简化了单个对象的交互逻辑；

缺点

• 中介者业务性太强，黑箱子的雏形。

其他

• 如果同事过多，逻辑过多，不管是否使用这种模式，循环调用这种事情都很难查找了。

使用场景

代码抽象良好，但是对象之间存在互相调用的情况建议使用中介者模式。

UML结构图：

代码实现

1.定义中介者，即Mediator

public interface Mediator {
    public void change(Colleague colleague);
}

2.中介者具体实现。即ConcreteMediator

public class ConcreteMediator implements Mediator {
    @Override
    public void change(Colleague colleague) {
        if (colleague instanceof ConcreteColleague1) {
            concreteColleague1Call((ConcreteColleague1) colleague);
        } else if (colleague instanceof ConcreteColleague2) {
            concreteColleague2Call((ConcreteColleague2) colleague);
        } else {
            throw new UnsupportedOperationException("unspported colleague");
        }
    }

    private void concreteColleague1Call(ConcreteColleague1 colleague) {
        colleague.call();
    }

    private void concreteColleague2Call(ConcreteColleague2 colleague) {
        colleague.call();
    }

}

3.定义同事抽象，即Colleague

public abstract class Colleague {
    protected Mediator mediator;
    protected Colleague(Mediator mediator) {
        this.mediator = mediator;
    }
}

4.具体同事具体实现，即ConcreteColleague1和ConcreteColleague2

public class ConcreteColleague1 extends Colleague {
    public ConcreteColleague1(Mediator mediator) {
        super(mediator);
    }

    public void doSmth() {
        System.out.println("ConcreteColleague1做了一些事情");
        mediator.change(this);
    }

    public void call() {
        System.out.println("外部调用ConcreteColleague1");
    }

}

public class ConcreteColleague2 extends Colleague {
    public ConcreteColleague2(Mediator mediator) {
        super(mediator);
    }

    public void doSmth() {
        System.out.println("ConcreteColleague2做了一些事情");
        mediator.change(this);
    }

    public void call() {
        System.out.println("外部调用ConcreteColleague2");
    }

}

5.测试调用，TestDrive

public class Run {
    public static void main(String[] args) {
        Mediator mediator = new ConcreteMediator();
        ConcreteColleague1 colleague1 = new ConcreteColleague1(mediator);
        ConcreteColleague2 colleague2 = new ConcreteColleague2(mediator);
        colleague1.doSmth();
        colleague2.doSmth();
    }
}