原文:
乐在其中设计模式(C#) - 备忘录模式(Memento Pattern)
作者： webabcd
介绍
在不破坏封装性的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态。这样以后就可将该对象恢复到保存的状态。
示例
有一个Message实体类，某个对象对它的操作有Insert()方法，只有在插入时间符合要求的情况下才能插入成功，因此要求可以保存和恢复Message对象的状态，插入失败后则恢复Message对象的状态，然后只更新时间，再次插入。
MessageModel
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Memento
{
/// <summary>
/// Message实体类（Memento）
/// </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; }
}
}
}
MessageModelCaretaker
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Memento
{
/// <summary>
/// Memento管理者（Caretaker）
/// </summary>
public class MessageModelCaretaker
{
private MessageModel _messageModel;
/// <summary>
/// Message实体对象（Memento）
/// </summary>
public MessageModel MessageModel
{
get { return _messageModel; }
set { _messageModel = value; }
}
}
}
SqlMessage
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Memento
{
/// <summary>
/// Sql方式操作Message（Originator）
/// </summary>
public class SqlMessage
{
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; }
}
/// <summary>
/// 插入Message
/// </summary>
/// <param name="mm">Message实体对象</param>
/// <returns></returns>
public bool Insert(MessageModel mm)
{
// 秒数可以被5整除时，则执行插入操作
if (mm.PublishTime.Second % 5 == 0)
{
// 代码略
return true;
}
else
{
return false;
}
}
/// <summary>
/// 保存Memento
/// </summary>
/// <returns></returns>
public MessageModel SaveMemento()
{
return new MessageModel(_message, _publishTime);
}
/// <summary>
/// 恢复Memento
/// </summary>
/// <param name="mm"></param>
public void RestoreMemento(MessageModel mm)
{
this._message = mm.Message;
this._publishTime = mm.PublishTime;
}
}
}
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.Memento;
public
partial
class
Memento : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
SqlMessage m = new SqlMessage();
m.Message = "Message内容";
m.PublishTime = DateTime.Now;
MessageModelCaretaker mmc = new MessageModelCaretaker();
mmc.MessageModel = m.SaveMemento();
bool bln = false;
while (!bln)
{
bln = m.Insert(new MessageModel(m.Message, m.PublishTime));
Response.Write(m.Message + " " + m.PublishTime.ToString() + " " + bln.ToString());
Response.Write("<br />");
if (!bln)
{
System.Threading.Thread.Sleep(1000);
m.RestoreMemento(mmc.MessageModel);
m.PublishTime = DateTime.Now;
}
}
}
}
运行结果
Message内容 2007-5-23 21:32:13 False
Message内容 2007-5-23 21:32:14 False
Message内容 2007-5-23 21:32:15 True
参考
http://www.dofactory.com/Patterns/PatternMemento.aspx
OK
[源码下载]
乐在其中设计模式(C#) - 备忘录模式(Memento Pattern)
作者： webabcd
介绍
在不破坏封装性的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态。这样以后就可将该对象恢复到保存的状态。
示例
有一个Message实体类，某个对象对它的操作有Insert()方法，只有在插入时间符合要求的情况下才能插入成功，因此要求可以保存和恢复Message对象的状态，插入失败后则恢复Message对象的状态，然后只更新时间，再次插入。
MessageModel
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Memento
{
/// <summary> /// Message实体类（Memento） /// </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; } } }}
MessageModelCaretaker
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Memento
{ /// <summary> /// Memento管理者（Caretaker） /// </summary> public class MessageModelCaretaker { private MessageModel _messageModel; /// <summary> /// Message实体对象（Memento） /// </summary> public MessageModel MessageModel { get { return _messageModel; } set { _messageModel = value; } } }}
SqlMessage
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Memento
{ /// <summary> /// Sql方式操作Message（Originator） /// </summary> public class SqlMessage { 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; } } /// <summary> /// 插入Message /// </summary> /// <param name="mm">Message实体对象</param> /// <returns></returns> public bool Insert(MessageModel mm) { // 秒数可以被5整除时，则执行插入操作 if (mm.PublishTime.Second % 5 == 0) { // 代码略 return true; } else { return false; } } /// <summary> /// 保存Memento /// </summary> /// <returns></returns> public MessageModel SaveMemento() { return new MessageModel(_message, _publishTime); } /// <summary> /// 恢复Memento /// </summary> /// <param name="mm"></param> public void RestoreMemento(MessageModel mm) { this._message = mm.Message; this._publishTime = mm.PublishTime; } }}
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.Memento;
public
partial
class
Memento : System.Web.UI.Page
{ protected void Page_Load(object sender, EventArgs e) { SqlMessage m = new SqlMessage(); m.Message = "Message内容"; m.PublishTime = DateTime.Now; MessageModelCaretaker mmc = new MessageModelCaretaker(); mmc.MessageModel = m.SaveMemento(); bool bln = false; while (!bln) { bln = m.Insert(new MessageModel(m.Message, m.PublishTime)); Response.Write(m.Message + " " + m.PublishTime.ToString() + " " + bln.ToString()); Response.Write("<br />"); if (!bln) { System.Threading.Thread.Sleep(1000); m.RestoreMemento(mmc.MessageModel); m.PublishTime = DateTime.Now; } } }}
运行结果
Message内容 2007-5-23 21:32:13 False
Message内容 2007-5-23 21:32:14 False
Message内容 2007-5-23 21:32:15 True
参考
http://www.dofactory.com/Patterns/PatternMemento.aspx
OK
[源码下载]
