设计模式——中介者模式

中介者模式一般用于解决多个对象或者多个系统之间相互关联,交互的复杂关系的问题!这种关系一般是网状结构,使用中介者模式,将这种网状结构转换为星型结构,降低各个对象之间的耦合度。

网状结构一般会导致系统复杂,可扩展性差,对象可复用程度降低!

中介者模式的缺点是中介者类比较复杂,而且一旦出问题可能会影响整个系统!

中介者模式的核心是中介者与其同事之间的双向绑定关系,即中介者拥有需要交互的所有同事,同事拥有中介者的引用!

下面以实际生产中的一个架构模型,说明中介者的应用:

1、中介者的抽象

/*
 * Copyright (c) 2017. Xiaomi.Co.Ltd All rights reserved
 */

package com.pt.mediator;

/**
 * @description 中介者抽象,申明一个联络方法
 * @author panteng
 * @date 17-2-22.
 */
public interface IMediator {
    /**
     * source和destination的类型设置为Object,实际上可以是中介者所有同事的抽象类
     * 在这个接口里实际上可以不传递source 和 destination参数,根据消息内容判断来源的目的
     * @param message
     */
    void contact(String message);
}
IMediator

2、所有同事的抽象(核心是需要拥有对中介者的引用)

/*
 * Copyright (c) 2017. Xiaomi.Co.Ltd All rights reserved
 */

package com.pt.mediator;

/**
 * @description 所有同事的抽象类,每一个同事都应该持有对中介者的引用
 * @author panteng
 * @date 17-2-22.
 */
public abstract class AbstractStation {
    String name;        //站点名
    IMediator mediator; //中介者

    public AbstractStation(){
    }

    public AbstractStation(String name, IMediator mediator){
        this.name = name;
        this.mediator = mediator;
    }

    public IMediator getMediator(){
        return mediator;
    }
    public void setMediator(IMediator mediator){
        this.mediator = mediator;
    }
}
AbstractStation

3、同事类

/*
 * Copyright (c) 2017. Xiaomi.Co.Ltd All rights reserved
 */

package com.pt.mediator;

/**
 * @description 负责扫描待充值/查询的订单
 * @author panteng
 * @date 17-2-22.
 */
public class AutoServer extends AbstractStation {
    public AutoServer(){
    }
    public AutoServer(String name, IMediator mediator){
        super(name, mediator);
    }
    void getMsg(String msg){
        System.out.println("AutoServer接收消息:" + msg);
        if ("待充值订单".equals(msg)) {
            this.sendMsg("请求充值");
        }
    }

    void sendMsg(String msg){
        System.out.println("AutoServer发送消息:" + msg);
        this.mediator.contact(msg);
    }
}
AutoServer
/*
 * Copyright (c) 2017. Xiaomi.Co.Ltd All rights reserved
 */

package com.pt.mediator;

/**
 * @description 负责业务处理
 * @author panteng
 * @date 17-2-22.
 */
public class AppServer extends AbstractStation {
    public AppServer(){
    }

    public AppServer(String name, IMediator mediator){
        super(name, mediator);
    }

    void getMsg(String msg){
        System.out.println("APPserver接收消息:" + msg);
        if ("请求充值".equals(msg)) {
            this.sendMsg("请发送至代理商");
        } else if (msg.indexOf("充值结果") > -1) {
            this.sendMsg("修改订单状态,充值中");
        }
    }

    void sendMsg(String msg){
        this.mediator.contact(msg);
    }
}
AppServer
/*
 * Copyright (c) 2017. Xiaomi.Co.Ltd All rights reserved
 */

package com.pt.mediator;

/**
 * @description 负责数据层访问
 * @author panteng
 * @date 17-2-22.
 */
public class DBPServer extends AbstractStation {
    public DBPServer(){
    }
    public DBPServer(String name, IMediator mediator){
        super(name, mediator);
    }

    void getMsg(String msg){
        System.out.println("DBPserver接收消息:" + msg);
        if ("查询待充值订单".equals(msg)) {
            this.sendMsg("待充值订单");
        } else if (msg.indexOf("修改订单状态") > -1) {
            System.out.println("DBP修改订单状态修改完毕");
        }
    }

    void sendMsg(String msg){
        System.out.println("DBPserver发送消息:" + msg);
        this.mediator.contact(msg);
    }
}
DBPServer
/*
 * Copyright (c) 2017. Xiaomi.Co.Ltd All rights reserved
 */

package com.pt.mediator;

/**
 * @description 负责向代理商发送充值/查询请求
 * @author panteng
 * @date 17-2-22.
 */
public class TomcatServer extends AbstractStation {
    public TomcatServer(){
    }
    public TomcatServer(String name, IMediator mediator){
        super(name, mediator);
    }

    void getMsg(String msg){
        System.out.println("TomcatServer接收消息:" + msg);
        System.out.println("TomcatServer向代理商请求充值");
        this.sendMsg("充值结果,充值成功... ...");
    }

    void sendMsg(String msg){
        this.mediator.contact(msg);
    }
}
TomcatServer

4、实际中介者

/*
 * Copyright (c) 2017. Xiaomi.Co.Ltd All rights reserved
 */

package com.pt.mediator;

/**
 * @description
 * @author panteng
 * @date 17-2-22.
 */
public class Mediator implements IMediator {
    AppServer appServer;
    AutoServer autoServer;
    DBPServer dbpServer;
    TomcatServer tomcatServer;

    public Mediator(){
    }
    public Mediator(AppServer appServer, AutoServer autoServer, DBPServer dbpServer, TomcatServer tomcatServer){
        this.appServer = appServer;
        this.autoServer = autoServer;
        this.dbpServer = dbpServer;
        this.tomcatServer = tomcatServer;

        this.appServer.setMediator(this);
        this.autoServer.setMediator(this);
        this.dbpServer.setMediator(this);
        this.tomcatServer.setMediator(this);
    }
    /**
     * source和destination的类型设置为Object,实际上可以是中介者所有同事的抽象类
     * @param message
     */
    public void contact(String message){
        if (message.indexOf("增") > -1 || message.indexOf("删") > -1 || message.indexOf("改") > -1 || message.indexOf("查") > -1) {
            this.dbpServer.getMsg(message);
            return;
        }
        if (message.indexOf("待") > -1) {
            this.autoServer.getMsg(message);
            return;
        }
        if ("请求充值".equals(message) || message.indexOf("充值结果") > -1) {
            this.appServer.getMsg(message);
        }
        if ("请发送至代理商".equals(message)) {
            this.tomcatServer.getMsg(message);
        }
    }
}
Mediator

5、测试

/*
 * Copyright (c) 2017. Xiaomi.Co.Ltd All rights reserved
 */

package com.pt.mediator;

import org.junit.Test;

/**
 * @description
 * @author panteng
 * @date 17-2-22.
 */
public class MediatorTest {
    @Test
    public void mediatorTest(){
        AppServer appServer = new AppServer();
        AutoServer autoServer = new AutoServer();
        DBPServer dbpServer = new DBPServer();
        TomcatServer tomcatServer = new TomcatServer();

        IMediator mediator = new Mediator(appServer, autoServer, dbpServer, tomcatServer);

        autoServer.sendMsg("查询待充值订单");
    }
}
MediatorTest

输出:

AutoServer发送消息:查询待充值订单
DBPserver接收消息:查询待充值订单
DBPserver发送消息:待充值订单
AutoServer接收消息:待充值订单
AutoServer发送消息:请求充值
APPserver接收消息:请求充值
TomcatServer接收消息:请发送至代理商
TomcatServer向代理商请求充值
APPserver接收消息:充值结果,充值成功... ...
DBPserver接收消息:修改订单状态,充值成功
DBP修改订单状态修改完毕

 

 

本例中,同事对象不需要关注其他同事对象,但这样可能会造成中介者的实现特别复杂!

实际应用中,对于发送消息的同事而言,知道其消息的接收者是谁,请求中介者时,需要将自己(消息的发送者)和目的同事(消息的接收者)传递给中介者,这样可方便中介者的实现,对外部逻辑影响并不大,因为消息发送者并不需要操作接受者的具体信息(如内部结构,方法等),只需要知道是谁即可。

posted @ 2017-02-22 10:03  沙中世界  阅读(287)  评论(0编辑  收藏  举报