行为模式---中介者模式

中介者模式

中介者模式解决将网状类图变为星状类图的过程，即原来每个类之间通信都需要持有对方，现在大家都不需要持有对方了，只需要持有中介者，而中介者持有大家即可
网状类图：

使用中介者模式后变为的星状类图：

其中AbstractColleague只是为了让每个子类进行Mediator设置而已，如图所示现在各个Colleague类编程了星状关系，所有的Colleague之间相互通信都需要经过ConcretorMediator，如果你只需要实现一种Mediator的话，这里Mediator接口可以省略
同事类Colleague：

public abstract class AbstractColleague {
    protected final Mediator mediator;

    public AbstractColleague(Mediator mediator) {
        this.mediator = mediator;
    }
}
public class Colleague1 extends AbstractColleague {
    //这里强制实现抽象类的构造方法传入中介者对象
    public Colleague1(Mediator mediator) {
        super(mediator);
        mediator.setColleague1(this);
    }

    public void receiveMessage(String message) {
        System.out.println(this.getClass().getName() + "收到:" + message);
    }

    //每一次通信其实调用的是中介者对象的方法，通过中介者调用其他同事类的方法
    public void sendMessageToColleague2(String message) {
        mediator.sendMessageToColleague2(message);
    }

    public void sendMessageToColleague3(String message) {
        mediator.sendMessageToColleague3(message);
    }
}
public class Colleague2 extends AbstractColleague {
    public Colleague2(Mediator mediator) {
        super(mediator);
        mediator.setColleague2(this);
    }

    public void receiveMessage(String message) {
        System.out.println(this.getClass().getName() + "收到:" + message);
    }

    public void sendMessageToColleague1(String message) {
        mediator.sendMessageToColleague1(message);
    }

    public void sendMessageToColleague3(String message) {
        mediator.sendMessageToColleague3(message);
    }
}
public class Colleague3 extends AbstractColleague {
    public Colleague3(Mediator mediator) {
        super(mediator);
        mediator.setColleague3(this);
    }

    public void receiveMessage(String message) {
        System.out.println(this.getClass().getName() + "收到:" + message);
    }

    public void sendMessageToColleague2(String message) {
        mediator.sendMessageToColleague2(message);
    }

    public void sendMessageToColleague3(String message) {
        mediator.sendMessageToColleague3(message);
    }
}

中介者类：

public interface Mediator {
    //这里我使用了直接设置同事类的方式，也可以不声明这三个接口，在使用的使用在一一设置
    public void setColleague1(Colleague1 colleague1);
    public void setColleague2(Colleague2 colleague2);
    public void setColleague3(Colleague3 colleague3);

    public void sendMessageToColleague1(String message);
    public void sendMessageToColleague2(String message);
    public void sendMessageToColleague3(String message);
}
public class ConcretorMediator implements Mediator {
    private Colleague1 colleague1;
    private Colleague2 colleague2;
    private Colleague3 colleague3;

    @Override
    public void setColleague1(Colleague1 colleague1) {
        this.colleague1 = colleague1;
    }

    @Override
    public void setColleague2(Colleague2 colleague2) {
        this.colleague2 = colleague2;
    }

    @Override
    public void setColleague3(Colleague3 colleague3) {
        this.colleague3 = colleague3;
    }

    @Override
    public void sendMessageToColleague1(String message) {
        colleague1.receiveMessage(message);
    }

    @Override
    public void sendMessageToColleague2(String message) {
        colleague2.receiveMessage(message);
    }

    @Override
    public void sendMessageToColleague3(String message) {
        colleague3.receiveMessage(message);
    }
}

客户端：

public class Client {
    public static void main(String[] args) {
        ConcretorMediator mediator = new ConcretorMediator();
        Colleague1 colleague1 = new Colleague1(mediator);
        Colleague2 colleague2 = new Colleague2(mediator);
        Colleague3 colleague3 = new Colleague3(mediator);

        colleague1.sendMessageToColleague2("hello 2");
        colleague1.sendMessageToColleague3("hello 3");
    }
}

输出：

Colleague2收到:hello 2
Colleague3收到:hello 3