23种设计模式之中介者模式(18)_发布订阅模式和中介者模式-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_36821220/article/details/109046140

中介者模式通过创建一个中介对象，集中管理多个对象之间的交互，降低了它们之间的耦合。然而，这可能导致中介者自身变得复杂。示例展示了如何使用Java实现中介者模式，包括抽象中介类、具体中介实例、同事抽象类以及两个具体的同事类。在Main类中，中介者协调两个同事类的消息传递。

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中介者模式（Mediator），用一个中介对象来封装一系列对象交互。中介者使各对象不需要显示地相互引用，从而使耦合松散，而且可以独立地改变他们之间的交互。
由于ConcreteMediator控制了集中化，于是就把交互复杂性变为了中介者的复杂性，这就使得中介者会变得比任何一个ConcreteColleague都复杂。
中介者模式的优点来自集中控制，其缺点也是他。

Mediator.java

/**
 * 抽象中介类
 */
public abstract class Mediator {
    public abstract void send(String message,Colleague colleague);
}

ConcreteMediator .java

/**
 * 中介实例类
 */
public class ConcreteMediator extends Mediator{

    private ConcreteColleague1 concreteColleague1;
    private ConcreteColleague2 concreteColleague2;

    public void setConcreteColleague1(ConcreteColleague1 concreteColleague1) {
        this.concreteColleague1 = concreteColleague1;
    }

    public void setConcreteColleague2(ConcreteColleague2 concreteColleague2) {
        this.concreteColleague2 = concreteColleague2;
    }

    @Override public void send(String message, Colleague colleague) {
        if (colleague == concreteColleague1) {
            concreteColleague2.notify(message);
        }else {
            concreteColleague1.notify(message);
        }
    }
}

Colleague.java

/**
 * 同事抽象类
 */
public abstract class Colleague {
    protected Mediator mediator;

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

ConcreteColleague1.java

public class ConcreteColleague1 extends Colleague {
    public ConcreteColleague1(Mediator mediator) {
        super(mediator);
    }
    public void send(String message) {
        mediator.send(message, this);
    }

    public void notify(String message) {
        System.out.println("同事1得到消息：" + message);
    }
}

ConcreteColleague2.java

public class ConcreteColleague2 extends Colleague {
    public ConcreteColleague2(Mediator mediator) {
        super(mediator);
    }
    public void send(String message) {
        mediator.send(message, this);
    }

    public void notify(String message) {
        System.out.println("同事2得到消息：" + message);
    }
}

Main.java

public class Main {
    public static void main(String[] args) {
        final ConcreteMediator m = new ConcreteMediator();
        final ConcreteColleague1 c1 = new ConcreteColleague1(m);
        final ConcreteColleague2 c2 = new ConcreteColleague2(m);

        m.setConcreteColleague1(c1);
        m.setConcreteColleague2(c2);

        c1.send("吃过饭了么");
        c2.send("没有呢");
    }
}