中介者模式

中介者模式是指用一个中介对象来封装一系列的对象交互。中介者使各对象不需要显式的相互作用从而使其耦合松散，而且可以独立的改变他们之间的交互。

中介者模式示例代码

下面例子代码实现了中介者模式。

Mediator.java

public abstract class Mediator {
    public abstract void send(String message, Colleague colleague);
}

ConcreteMediator.java

public class ConcreteMediator extends Mediator {
    private Colleague colleagueA;
    private Colleague colleagueB;

    public void setColleagueA(Colleague colleagueA) {
        this.colleagueA = colleagueA;
    }

    public void setColleagueB(Colleague colleagueB) {
        this.colleagueB = colleagueB;
    }

    @Override
    public void send(String message, Colleague colleague) {
        if (colleague == colleagueA) {
            colleagueB.inform(message);
        } else {
            colleagueA.inform(message);
        }
    }
}

Colleague.java

public abstract class Colleague {
    protected Mediator mediator;

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

    public abstract void send(String message);

    public abstract void inform(String message);
}

ColleagueA.java

public class ColleagueA extends Colleague {
    public ColleagueA(Mediator mediator) {
        super(mediator);
    }

    @Override
    public void send(String message) {
        mediator.send(message, this);
    }

    @Override
    public void inform(String message) {
        System.out.println("colleagueA" + message);
    }
}

ColleagueB.java

public class ColleagueB extends Colleague {
    public ColleagueB(Mediator mediator) {
        super(mediator);
    }

    @Override
    public void send(String message) {
        mediator.send(message, this);
    }

    @Override
    public void inform(String message) {
        System.out.println("colleagueB" + message);
    }
}

Main.java

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

        Colleague colleagueA = new ColleagueA(mediator);
        Colleague colleagueB = new ColleagueB(mediator);

        mediator.setColleagueA(colleagueA);
        mediator.setColleagueB(colleagueB);

        colleagueA.send("hello1");
        colleagueB.send("hello2");
    }
}

上述代码使用一个Mediator作为中介者负责为两个Colleague类传递信息。其实现是两个Colleague包含了同一个Mediator属性，因此调用Mediator中的方法就行了。

中介者模式的优缺点

中介者的出现减少了系统各个实体之间的耦合，但是中介者使得系统的控制变得集中化，交互的复杂性变为了中介者的复杂性，中介者可能再次变得难以维护。中介者模式通常应用于一组对象，以定义良好但是复杂的方式进行通信的场合，以及想定制一个分布在多个类中的行为，而又不想生成太多子类的场合。

作者：Gacfox
版权声明：本网站为非盈利性质，文章如非特殊说明均为原创，版权遵循知识共享协议CC BY-NC-ND 4.0进行授权，转载必须署名，禁止用于商业目的或演绎修改后转载。
Copyright © 2017-2024 Gacfox All Rights Reserved.
Build with NextJS | Sitemap