二十四种设计模式：中介者模式(Mediator Pattern)

中介者模式(Mediator Pattern)

介绍
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地相互引用，从而使其耦合松散，而且可以独立地改变它们之间的交互。

示例
有一个Message实体类，某个对象对它的操作有Send()和Insert()方法，现在用一个中介对象来封装这一系列的对象交互。

　　MessageModel

using System;
using System.Collections.Generic;
using System.Text;

namespace Pattern.Mediator
{
    /// <summary>
    /// Message实体类
    /// </summary>
    public class MessageModel
    {
        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="msg">Message内容</param>
        /// <param name="pt">Message发布时间</param>
        public MessageModel(string msg, DateTime pt)
        {
            this._message = msg;
            this._publishTime = pt;
        }

        private string _message;
        /// <summary>
        /// Message内容
        /// </summary>
        public string Message
        {
            get { return _message; }
            set { _message = value; }
        }

        private DateTime _publishTime;
        /// <summary>
        /// Message发布时间
        /// </summary>
        public DateTime PublishTime
        {
            get { return _publishTime; }
            set { _publishTime = value; }
        }
    }
}

　　AbstractMessageMediator

using System;
using System.Collections.Generic;
using System.Text;

namespace Pattern.Mediator
{
    /// <summary>
    /// 抽象中介者（Mediator）
    /// </summary>
    public abstract class AbstractMessageMediator
    {
        /// <summary>
        /// 注册一个操作Message的对象
        /// </summary>
        /// <param name="AbstractMessage">AbstractMessage</param>
        public abstract void Register(AbstractMessage AbstractMessage);

        /// <summary>
        /// 发送Message
        /// </summary>
        /// <param name="from">来自UserId</param>
        /// <param name="to">发送到UserId</param>
        /// <param name="mm">Message实体对象</param>
        /// <returns></returns>
        public abstract string Send(string from, string to, MessageModel mm);
    }
}

　　MessageMediator

using System;
using System.Collections.Generic;
using System.Text;

namespace Pattern.Mediator
{
    /// <summary>
    /// 中介者（ConcreteMediator）
    /// </summary>
    public class MessageMediator : AbstractMessageMediator
    {
        private Dictionary<string, AbstractMessage> _dictionary = new Dictionary<string, AbstractMessage>();

        /// <summary>
        /// 注册一个操作Message的对象
        /// </summary>
        /// <param name="abstractMessage">AbstractMessage</param>
        public override void Register(AbstractMessage abstractMessage)
        {
            if (!_dictionary.ContainsKey(abstractMessage.UserId))
            {
                _dictionary.Add(abstractMessage.UserId, abstractMessage);
            }

            abstractMessage.AbstractMessageMediator = this;
        }

        /// <summary>
        /// 发送Message
        /// </summary>
        /// <param name="from">来自UserId</param>
        /// <param name="to">发送到UserId</param>
        /// <param name="mm">Message实体对象</param>
        /// <returns></returns>
        public override string Send(string from, string to, MessageModel mm)
        {
            AbstractMessage abstractMessage = _dictionary[to];
            if (abstractMessage != null)
            {
                return abstractMessage.Insert(from, mm);
            }
            else
            {
                return null;
            }
        }
    }
}

　　AbstractMessage

using System;
using System.Collections.Generic;
using System.Text;

namespace Pattern.Mediator
{
    /// <summary>
    /// 操作Message抽象类（Colleague）
    /// </summary>
    public abstract class AbstractMessage
    {
        private AbstractMessageMediator _abstractMessageMediator;
        private string _userId;

        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="userId">UserId</param>
        public AbstractMessage(string userId)
        {
            this._userId = userId;
        }

        /// <summary>
        /// UserId
        /// </summary>
        public string UserId
        {
            get { return _userId; }
        }

        /// <summary>
        /// 中介者
        /// </summary>
        public AbstractMessageMediator AbstractMessageMediator
        {
            get { return _abstractMessageMediator; }
            set { _abstractMessageMediator = value; }
        }

        /// <summary>
        /// 发送Message（由客户端调用）
        /// </summary>
        /// <param name="to">发送到UserId</param>
        /// <param name="mm">Message实体对象</param>
        /// <returns></returns>
        public string Send(string to, MessageModel mm)
        {
            return _abstractMessageMediator.Send(_userId, to, mm);
        }

        /// <summary>
        /// 接受Message（由中介者调用）
        /// </summary>
        /// <param name="from">来自UserId</param>
        /// <param name="mm">Message实体对象</param>
        /// <returns></returns>
        public abstract string Insert(string from, MessageModel mm);
    }
}

　　SqlMessage

using System;
using System.Collections.Generic;
using System.Text;

namespace Pattern.Mediator
{
    /// <summary>
    /// Sql方式操作Message（ConcreteColleague）
    /// </summary>
    public class SqlMessage : AbstractMessage
    {
        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="userId">UserId</param>
        public SqlMessage(string userId)
            : base(userId)
        {

        }

        /// <summary>
        /// 接受Message（由中介者调用）
        /// </summary>
        /// <param name="from">来自UserId</param>
        /// <param name="mm">Message实体对象</param>
        /// <returns></returns>
        public override string Insert(string from, MessageModel mm)
        {
            return "Sql方式插入Message（" + from + "发送给" + base.UserId + "）"
                + " - 内容：" + mm.Message
                + " - 时间：" + mm.PublishTime.ToString();
        }
    }
}

　　XmlMessage

using System;
using System.Collections.Generic;
using System.Text;

namespace Pattern.Mediator
{
    /// <summary>
    /// Xml方式操作Message（ConcreteColleague）
    /// </summary>
    public class XmlMessage : AbstractMessage
    {
        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="userId">UserId</param>
        public XmlMessage(string userId)
            : base(userId)
        {

        }

        /// <summary>
        /// 接受Message（由中介者调用）
        /// </summary>
        /// <param name="from">来自UserId</param>
        /// <param name="mm">Message实体对象</param>
        /// <returns></returns>
        public override string Insert(string from, MessageModel mm)
        {
            return "Xml方式插入Message（" + from + "发送给" + base.UserId + "）"
                + " - 内容：" + mm.Message
                + " - 时间：" + mm.PublishTime.ToString();
        }
    }
}

　　Test

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

using Pattern.Mediator;

public partial class Mediator : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        AbstractMessageMediator messageMediator = new MessageMediator();

        AbstractMessage user1 = new SqlMessage("user1");
        AbstractMessage user2 = new SqlMessage("user2");
        AbstractMessage user3 = new XmlMessage("user3");
        AbstractMessage user4 = new XmlMessage("user4");

        messageMediator.Register(user1);
        messageMediator.Register(user2);
        messageMediator.Register(user3);
        messageMediator.Register(user4);

        Response.Write(user1.Send("user2", new MessageModel("你好！", DateTime.Now)));
        Response.Write("<br />");
        Response.Write(user2.Send("user1", new MessageModel("我不好！", DateTime.Now)));
        Response.Write("<br />");
        Response.Write(user1.Send("user2", new MessageModel("不好就不好吧。", DateTime.Now)));
        Response.Write("<br />");
        Response.Write(user3.Send("user4", new MessageModel("吃了吗？", DateTime.Now)));
        Response.Write("<br />");
        Response.Write(user4.Send("user3", new MessageModel("没吃，你请我？", DateTime.Now)));
        Response.Write("<br />");
        Response.Write(user3.Send("user4", new MessageModel("不请。", DateTime.Now)));
        Response.Write("<br />");
    }
}

　　运行结果
　　Sql方式插入Message（user1发送给user2） - 内容：你好！ - 时间：2007-5-19 23:43:19
　　Sql方式插入Message（user2发送给user1） - 内容：我不好！ - 时间：2007-5-19 23:43:19
　　Sql方式插入Message（user1发送给user2） - 内容：不好就不好吧。 - 时间：2007-5-19 23:43:19
　　Xml方式插入Message（user3发送给user4） - 内容：吃了吗？ - 时间：2007-5-19 23:43:19
　　Xml方式插入Message（user4发送给user3） - 内容：没吃，你请我？ - 时间：2007-5-19 23:43:19
　　Xml方式插入Message（user3发送给user4） - 内容：不请。 - 时间：2007-5-19 23:43:19