中介者模式

一、作用：降低类与类之间的耦合程度，当A和B有双向的关系时，就产生了较强的耦合，这时候引入一个中介者的类，A与B都只和这个中介者类相关，由中介者类来控制A与B的关系，这样就完成了解耦。

二、例子：

有两种工人workera 和workerb，他们需要一起工作，如果不使用中介者模式，那么就需要两个类，WorkerA和WorkerB，他们之间相互依赖。使用中介者模式时，如下：

先定义一个抽象工作类：

public abstract class AbstractWorker {
IMediator mediator ;
public AbstractWorker(IMediator mediator) {
this.mediator = mediator ;
}
abstract void work();
}

WorkerA：

public class WorkerA extends AbstractWorker {
public WorkerA(IMediator mediator) {
super(mediator);
}
@Override
void work() {
System.out.println("worka is working!");
}

}

WorkerB:

public class WorkerB extends AbstractWorker{

public WorkerB(IMediator mediator) {
super(mediator);
}
@Override
void work() {
System.out.println("workb is working");
}

}

IMediator接口:

public abstract class AbstractWorker {
IMediator mediator ;
public AbstractWorker(IMediator mediator) {
this.mediator = mediator ;
}
abstract void work();
}

Mediator实现类：

public class Mediator implements IMediator{

private WorkerA workera ;
private WorkerB workerb ;

@Override
public void createWorkers(WorkerA workerA,WorkerB workerB) {
this.workera = workerA ;
this.workerb = workerB ;
}

@Override
public void beginWork() {
this.workera.work();
this.workerb.work();
}

}

测试类：

public class Test {
public static void main(String[] args) {
IMediator mediator = new Mediator();
WorkerA workerA = new WorkerA(mediator);
WorkerB workerB = new WorkerB(mediator);
mediator.createWorkers(workerA, workerB);
mediator.beginWork();
}
}

运行结果：

worka is working!

workb is working