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