二十四种设计模式：桥接模式(Bridge Pattern)

桥接模式(Bridge Pattern)

介绍
将抽象部分与它的实现部分分离，使它们都可以独立地变化。

示例
有一个Message实体类，对它的操作有Insert()和Get()方法，现在使这些操作的抽象部分和实现部分分离。

　　MessageModel

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

namespace Pattern.Bridge
{
    /// <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; }
        }
    }
}

　　Message

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

namespace Pattern.Bridge
{
    /// <summary>
    /// 操作Message（Abstraction）
    /// </summary>
    public class Message
    {
        private AbstractMessage _abstractMessage;
        /// <summary>
        /// 操作Message（Implementor）
        /// </summary>
        public AbstractMessage AbstractMessage
        {
            get { return _abstractMessage; }
            set { _abstractMessage = value; }
        }

        /// <summary>
        /// 获取Message
        /// </summary>
        /// <returns></returns>
        public virtual List<MessageModel> Get()
        {
            return _abstractMessage.Get();
        }

        /// <summary>
        /// 插入Message
        /// </summary>
        /// <param name="mm">Message实体对象</param>
        /// <returns></returns>
        public virtual bool Insert(MessageModel mm)
        {
            return _abstractMessage.Insert(mm);
        }
    }
}

　　MyMessage

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

namespace Pattern.Bridge
{
    /// <summary>
    /// 操作Message（RefinedAbstraction）
    /// </summary>
    public class MyMessage : Message
    {
        /// <summary>
        /// 获取Message
        /// </summary>
        /// <returns></returns>
        public override List<MessageModel> Get()
        {
            List<MessageModel> l = base.Get();

            foreach (MessageModel mm in l)
            {
                mm.Message += "（RefinedAbstraction）";
            }

            return l;
        }
    }
}

　　AbstractMessage

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

namespace Pattern.Bridge
{
    /// <summary>
    /// 操作Message（Implementor）
    /// </summary>
    public abstract class AbstractMessage
    {
        /// <summary>
        /// 获取Message
        /// </summary>
        /// <returns></returns>
        public abstract List<MessageModel> Get();

        /// <summary>
        /// 插入Message
        /// </summary>
        /// <param name="mm">Message实体对象</param>
        /// <returns></returns>
        public abstract bool Insert(MessageModel mm);
    }
}

　　SqlMessage

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

namespace Pattern.Bridge
{
    /// <summary>
    /// Sql方式操作Message（ConcreteImplementor）
    /// </summary>
    public class SqlMessage : AbstractMessage
    {
        /// <summary>
        /// 获取Message
        /// </summary>
        /// <returns></returns>
        public override List<MessageModel> Get()
        {
            List<MessageModel> l = new List<MessageModel>();
            l.Add(new MessageModel("SQL方式获取Message", DateTime.Now));

            return l;
        }

        /// <summary>
        /// 插入Message
        /// </summary>
        /// <param name="mm">Message实体对象</param>
        /// <returns></returns>
        public override bool Insert(MessageModel mm)
        {
            // 代码略
            return true;
        }
    }
}

　　XmlMessage

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

namespace Pattern.Bridge
{
    /// <summary>
    /// Xml方式操作Message（ConcreteImplementor）
    /// </summary>
    public class XmlMessage : AbstractMessage
    {
        /// <summary>
        /// 获取Message
        /// </summary>
        /// <returns></returns>
        public override List<MessageModel> Get()
        {
            List<MessageModel> l = new List<MessageModel>();
            l.Add(new MessageModel("XML方式获取Message", DateTime.Now));

            return l;
        }

        /// <summary>
        /// 插入Message
        /// </summary>
        /// <param name="mm">Message实体对象</param>
        /// <returns></returns>
        public override bool Insert(MessageModel mm)
        {
            // 代码略
            return true;
        }
    }
}

　　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.Bridge;

public partial class Bridge : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        MyMessage m = new MyMessage();

        m.AbstractMessage = new SqlMessage();

        Response.Write(m.Insert(new MessageModel("插入", DateTime.Now)));
        Response.Write("<br />");
        Response.Write(m.Get()[0].Message + " " + m.Get()[0].PublishTime.ToString());
        Response.Write("<br />");

        m.AbstractMessage = new XmlMessage();

        Response.Write(m.Insert(new MessageModel("插入", DateTime.Now)));
        Response.Write("<br />");
        Response.Write(m.Get()[0].Message + " " + m.Get()[0].PublishTime.ToString());
    }
}

　　运行结果
　　True
　　SQL方式获取Message（RefinedAbstraction） 2007-5-13 19:11:19
　　True
　　XML方式获取Message（RefinedAbstraction） 2007-5-13 19:11:19