设计模式 - State Pattern(状态模式)

设计模式 - State Pattern(状态模式)

[源码下载]

[align=center]设计模式 - State Pattern(状态模式)
[/align]

作者：webabcd

介绍
允许一个对象在其内部状态改变时改变它的行为。对象看起来似乎修改了它所属的类。

示例
有一个Message实体类，对它的操作有Insert()和Get()方法，持久化数据在SqlServer数据库中或Xml文件里。在对象内部可以根据用户的不同选择不同的数据持久化方案。



MessageModel


using System;


using System.Collections.Generic;


using System.Text;




namespace Pattern.State






{




/**//// <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; }


}


}


}



AbstractMessageState


using System;


using System.Collections.Generic;


using System.Text;




namespace Pattern.State






{




/**//// <summary>


/// 状态模式抽象类


/// </summary>


public abstract class AbstractMessageState






{




/**//// <summary>


/// Context类型


/// </summary>


protected Message _message;






/**//// <summary>


/// Context类型属性


/// </summary>


public Message Message






{




get

{ return _message; }




set

{ _message = value; }


}






/**//// <summary>


/// 改变状态


/// </summary>


public abstract void StateChangeCheck();






/**//// <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);


}


}



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>


/// 构造函数


/// </summary>


/// <param name="message">Context类型参数</param>


public XmlMessage(Message message)






{


this._message = message;


}






/**//// <summary>


/// 改变状态


/// </summary>


public override void StateChangeCheck()






{


// 如果UserId是admin则变换状态为SqlMessage


if (this._message.UserId == "admin")






{


this._message.AbstractMessageState = new SqlMessage(this._message);


}


}






/**//// <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;


}


}


}



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>


/// 构造函数


/// </summary>


/// <param name="message">Context类型参数</param>


public SqlMessage(Message message)






{


this._message = message;


}






/**//// <summary>


/// 改变状态


/// </summary>


public override void StateChangeCheck()






{




}






/**//// <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;


}


}


}



Message


using System;


using System.Collections.Generic;


using System.Text;




namespace Pattern.State






{




/**//// <summary>


/// Context类


/// </summary>


public class Message






{




/**//// <summary>


/// 类型为状态模式抽象类的私有变量


/// </summary>


private AbstractMessageState _abstractMessageState;






/**//// <summary>


/// 类型为状态模式抽象类的属性


/// </summary>


public AbstractMessageState AbstractMessageState






{




get

{ return _abstractMessageState; }




set

{ _abstractMessageState = value; }


}






/**//// <summary>


/// UserId私有变量


/// </summary>


private string _userId;






/**//// <summary>


/// UserId


/// </summary>


public string UserId






{




get

{ return _userId; }




set

{ _userId = value; }


}






/**//// <summary>


/// 构造函数


/// </summary>


/// <param name="userId">UserId</param>


public Message(string userId)






{


this._userId = userId;




_abstractMessageState = new XmlMessage(this);


}






/**//// <summary>


/// 获取Message


/// </summary>


/// <returns></returns>


public List<MessageModel> Get()






{


// 修改状态


_abstractMessageState.StateChangeCheck();




return _abstractMessageState.Get();


}






/**//// <summary>


/// 插入Message


/// </summary>


/// <param name="mm">Message实体对象</param>


/// <returns></returns>


public bool Insert(MessageModel mm)






{


// 修改状态


_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 />");


}


}



运行结果
True
SQL方式获取Message 2007-3-6 22:58:17
True
XML方式获取Message 2007-3-6 22:58:17

OK
[源码下载]