[译]Java 设计模式之中介者

(文章翻译自Java Design Pattern: Mediator)

中介者设计模式被用于一组的同事进行协作。这些同事不彼此进行直接的交流联系，但是是通过中介者。

在下面的例子中，A同事想去说话，B同事先去打架。当他们做些事情时候他们调用了中介者的方法去做这些。

中介者模式类图

中介者Java代码

package designpatterns.mediator;

interface IMediator {
	public void fight();
	public void talk();
	public void registerA(ColleagueA a);
	public void registerB(ColleagueB a);
}

//concrete mediator
class ConcreteMediator implements IMediator{

	ColleagueA talk;
	ColleagueB fight;

	public void registerA(ColleagueA a){
		talk = a;
	}

	public void registerB(ColleagueB b){
		fight = b;
	}

	public void fight(){
		System.out.println("Mediator is fighting");
		//let the fight colleague do some stuff
	}

	public void talk(){
		System.out.println("Mediator is talking");
		//let the talk colleague do some stuff
	}
}

abstract class Colleague {
	IMediator mediator;
	public abstract void doSomething();
}

//concrete colleague
class ColleagueA extends Colleague {

	public ColleagueA(IMediator mediator) {
		this.mediator = mediator;
	}

	@Override
	public void doSomething() {
		this.mediator.talk();
		this.mediator.registerA(this);
	}
}

//concrete colleague
class ColleagueB extends Colleague {
	public ColleagueB(IMediator mediator) {
		this.mediator = mediator;
		this.mediator.registerB(this);
	}

	@Override
	public void doSomething() {
		this.mediator.fight();
	}
}

public class MediatorTest {
	public static void main(String[] args) {
		IMediator mediator = new ConcreteMediator();

		ColleagueA talkColleague = new ColleagueA(mediator);
		ColleagueB fightColleague = new ColleagueB(mediator);

		talkColleague.doSomething();
		fightColleague.doSomething();
	}
}

在其他的行为模式中，观察者是和中介者最相似的。你可以读下观察者模式来比较下他们的不同。