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();
}
}