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介紹
允許一個對象在其內部狀態改變時改變它的行為。對象看起來似乎修改了它所屬的類。
示例
有一個Message實體類，對它的操作有Insert()和Get()方法，持久化數據在SqlServer數據庫中或Xml文件裡。在對象內部可以根據用戶的不同選擇不同的數據持久化方案。
MessageModel
using System;
using System.Collections.Generic;
using System.Text;
namespace Pattern.State
{
/**//// <summary>
/// Message實體類
/// </summary>
public class MessageModel
{
/**//// <summary>
/// 構造函數
/// </summary>
/// <param name="msg">Message內容</param>
/// <param name="pt">Message發布時間</param>
public MessageModel(string msg, DateTime pt)
{
this._message = msg;
this._publishTime = pt;
}
private string _message;
/**//// <summary>
/// Message內容
/// </summary>
public string Message
{
get { return _message; }
set { _message = value; }
}
private DateTime _publishTime;
/**//// <summary>
/// Message發布時間
/// </summary>
public DateTime PublishTime
{
get { return _publishTime; }
set { _publishTime = value; }
}
}
}
AbstractMessageState
using System;
using System.Collections.Generic;
using System.Text;
namespace Pattern.State
{
/**//// <summary>
/// 狀態模式抽象類
/// </summary>
public abstract class AbstractMessageState
{
/**//// <summary>
/// Context類型
/// </summary>
protected Message _message;
/**//// <summary>
/// Context類型屬性
/// </summary>
public Message Message
{
get { return _message; }
set { _message = value; }
}
/**//// <summary>
/// 改變狀態
/// </summary>
public abstract void StateChangeCheck();
/**//// <summary>
/// 獲取Message
/// </summary>
/// <returns></returns>
public abstract List<MessageModel> Get();
/**//// <summary>
/// 插入Message
/// </summary>
/// <param name="mm">Message實體對象</param>
/// <returns></returns>
public abstract bool Insert(MessageModel mm);
}
}
XmlMessage
using System;
using System.Collections.Generic;
using System.Text;
namespace Pattern.State
{
/**//// <summary>
/// Xml方式操作Message
/// </summary>
public class XmlMessage : AbstractMessageState
{
/**//// <summary>
/// 構造函數
/// </summary>
/// <param name="message">Context類型參數</param>
public XmlMessage(Message message)
{
this._message = message;
}
/**//// <summary>
/// 改變狀態
/// </summary>
public override void StateChangeCheck()
{
// 如果UserId是admin則變換狀態為SqlMessage
if (this._message.UserId == "admin")
{
this._message.AbstractMessageState = new SqlMessage(this._message);
}
}
/**//// <summary>
/// 獲取Message
/// </summary>
/// <returns></returns>
public override List<MessageModel> Get()
{
List<MessageModel> l = new List<MessageModel>();
l.Add(new MessageModel("XML方式獲取Message", DateTime.Now));
return l;
}
/**//// <summary>
/// 插入Message
/// </summary>
/// <param name="mm">Message實體對象</param>
/// <returns></returns>
public override bool Insert(MessageModel mm)
{
// 代碼略
return true;
}
}
}
SqlMessage
using System;
using System.Collections.Generic;
using System.Text;
namespace Pattern.State
{
/**//// <summary>
/// Sql方式操作Message
/// </summary>
public class SqlMessage : AbstractMessageState
{
/**//// <summary>
/// 構造函數
/// </summary>
/// <param name="message">Context類型參數</param>
public SqlMessage(Message message)
{
this._message = message;
}
/**//// <summary>
/// 改變狀態
/// </summary>
public override void StateChangeCheck()
{
}
/**//// <summary>
/// 獲取Message
/// </summary>
/// <returns></returns>
public override List<MessageModel> Get()
{
List<MessageModel> l = new List<MessageModel>();
l.Add(new MessageModel("SQL方式獲取Message", DateTime.Now));
return l;
}
/**//// <summary>
/// 插入Message
/// </summary>
/// <param name="mm">Message實體對象</param>
/// <returns></returns>
public override bool Insert(MessageModel mm)
{
// 代碼略
return true;
}
}
}
Message
using System;
using System.Collections.Generic;
using System.Text;
namespace Pattern.State
{
/**//// <summary>
/// Context類
/// </summary>
public class Message
{
/**//// <summary>
/// 類型為狀態模式抽象類的私有變量
/// </summary>
private AbstractMessageState _abstractMessageState;
/**//// <summary>
/// 類型為狀態模式抽象類的屬性
/// </summary>
public AbstractMessageState AbstractMessageState
{
get { return _abstractMessageState; }
set { _abstractMessageState = value; }
}
/**//// <summary>
/// UserId私有變量
/// </summary>
private string _userId;
/**//// <summary>
/// UserId
/// </summary>
public string UserId
{
get { return _userId; }
set { _userId = value; }
}
/**//// <summary>
/// 構造函數
/// </summary>
/// <param name="userId">UserId</param>
public Message(string userId)
{
this._userId = userId;
_abstractMessageState = new XmlMessage(this);
}
/**//// <summary>
/// 獲取Message
/// </summary>
/// <returns></returns>
public List<MessageModel> Get()
{
// 修改狀態
_abstractMessageState.StateChangeCheck();
return _abstractMessageState.Get();
}
/**//// <summary>
/// 插入Message
/// </summary>
/// <param name="mm">Message實體對象</param>
/// <returns></returns>
public bool Insert(MessageModel mm)
{
// 修改狀態
_abstractMessageState.StateChangeCheck();
return _abstractMessageState.Insert(mm);
}
}
}
client
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.State;
public partial class State : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
Message m = new Message("admin");
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 = new Message("user");
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 />");
}
}
運行結果
True
SQL方式獲取Message 2007-3-6 22:58:17
True
XML方式獲取Message 2007-3-6 22:58:17
參考
http://www.dofactory.com/Patterns/PatternState.aspx
OK
