设计模式 - Command Pattern(命令模式)

设计模式 - Command Pattern(命令模式)

设计模式 - Command Pattern(命令模式)

作者：webabcd

介绍
将一个请求封装为一个对象，从而使你可用不同的请求对客户进行参数化；对请求排队或记录请求日志，以及支持可取消的操作。

示例
有一个Message实体类，某个类对它的操作有Insert()和Delete()方法。现在要求可以对之前的所有操作做撤销和重复。



MessageModel


using System;


using System.Collections.Generic;


using System.Text;




namespace Pattern.Command






{




/**//// <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; }


}


}


}

Action


using System;


using System.Collections.Generic;


using System.Text;




namespace Pattern.Command






{




/**//// <summary>


/// enum


/// 定义操作的两种方法Insert和Delete


/// </summary>


public enum Action






{




/**//// <summary>


/// Insert


/// </summary>


Insert,






/**//// <summary>


/// Delete


/// </summary>


Delete


}


}



SqlMessage


using System;


using System.Collections.Generic;


using System.Text;




namespace Pattern.Command






{




/**//// <summary>


/// 接收者（Receiver）角色


/// Sql方式操作Message


/// </summary>


public class SqlMessage






{




/**//// <summary>


/// 操作


/// </summary>


/// <param name="action">操作的方法</param>


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


public void Operation(Action action, MessageModel mm)






{


switch (action)






{


case Action.Insert :


Insert(mm);


break;


case Action.Delete :


Delete(mm);


break;


}


}






/**//// <summary>


/// 插入Message


/// </summary>


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


private void Insert(MessageModel mm)






{


// 代码略


}






/**//// <summary>


/// 删除Message


/// </summary>


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


private void Delete(MessageModel mm)






{


// 代码略


}


}


}



ICommand


using System;


using System.Collections.Generic;


using System.Text;




namespace Pattern.Command






{




/**//// <summary>


/// 命令（Command）角色


/// </summary>


public interface ICommand






{




/**//// <summary>


/// 执行


/// </summary>


/// <returns>操作的方法及操作的信息</returns>


string Execute();






/**//// <summary>


/// 取消执行


/// </summary>


/// <returns>操作的方法及操作的信息</returns>


string UnExecute();


}


}



SqlMessageCommand


using System;


using System.Collections.Generic;


using System.Text;




namespace Pattern.Command






{




/**//// <summary>


/// 具体命令（ConcreteCommand）角色


/// </summary>


public class SqlMessageCommand : ICommand






{




/**//// <summary>


/// 操作的方法


/// </summary>


private Action _action;






/**//// <summary>


/// Message实体对象


/// </summary>


private MessageModel _mm;






/**//// <summary>


/// 构造函数


/// </summary>


/// <param name="action">操作的方法</param>


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


public SqlMessageCommand(Action action, MessageModel mm)






{


this._action = action;


this._mm = mm;


}






/**//// <summary>


/// 执行


/// </summary>


/// <returns>操作的方法及操作的信息</returns>


public string Execute()






{


new SqlMessage().Operation(_action, _mm);




return _action.ToString() + "：" + _mm.Message;


}






/**//// <summary>


/// 取消执行（调用一个方法，以决定取消执行的算法）


/// </summary>


/// <returns>操作的方法及操作的信息</returns>


public string UnExecute()






{


_action = GetUndoAction(_action);


new SqlMessage().Operation(_action, _mm);




return _action.ToString() + "：" + _mm.Message;


}






/**//// <summary>


/// 获得取消执行的算法


/// </summary>


/// <param name="action">操作的方法</param>


/// <returns></returns>


private Action GetUndoAction(Action action)






{


Action undo;




switch (action)






{


case Action.Insert :


undo = Action.Delete;


break;


case Action.Delete :


undo = Action.Insert;


break;


// 这句没啥用


default :


undo = Action.Insert;


break;


}




return undo;


}


}


}



Message


using System;


using System.Collections.Generic;


using System.Text;




namespace Pattern.Command






{




/**//// <summary>


/// 请求者（Invoker）角色


/// </summary>


public class Message






{




/**//// <summary>


/// 命令集合（保存每次操作）


/// </summary>


private List<ICommand> _listCommand = new List<ICommand>();






/**//// <summary>


/// 命令集合中当前要执行的命令的索引


/// </summary>


private int current = 0;






/**//// <summary>


/// 执行Sql


/// </summary>


/// <param name="action">操作的方法</param>


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


/// <returns>操作的方法及操作的信息</returns>


public string Do(Action action, MessageModel mm)






{


string rtn = "";




ICommand cmd = new SqlMessageCommand(action, mm);


rtn = cmd.Execute();




_listCommand.Add(cmd);


current++;




return rtn;


}






/**//// <summary>


/// 撤销


/// </summary>


/// <param name="levels">执行撤销操作的次数</param>


/// <returns>操作的方法及操作的信息（用空格分开多条记录）</returns>


public string Undo(int levels)






{


string rtn = "";




for (int i = 0; i < levels; i++)






{


if (current > 0)






{


ICommand cmd = _listCommand[--current];


rtn += cmd.UnExecute() + " ";


}


}




return rtn;


}






/**//// <summary>


/// 重复


/// </summary>


/// <param name="levels">执行重复操作的次数</param>


/// <returns>操作的方法及操作的信息（用空格分开多条记录）</returns>


public string Redo(int levels)






{


string rtn = "";




for (int i = 0; i < levels; i++)






{


if (current < _listCommand.Count - 1)






{


ICommand cmd = _listCommand[current++];


rtn += cmd.UnExecute() + " ";


}


}




return rtn;


}


}


}



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.Command;




public partial class Command : System.Web.UI.Page






{


protected void Page_Load(object sender, EventArgs e)






{


Message m = new Message();




Response.Write("操作");


Response.Write("<br />");


Response.Write(m.Do(Action.Insert, new MessageModel("第1条", DateTime.Now)));


Response.Write("<br />");


Response.Write(m.Do(Action.Insert, new MessageModel("第2条", DateTime.Now)));


Response.Write("<br />");


Response.Write(m.Do(Action.Insert, new MessageModel("第3条", DateTime.Now)));


Response.Write("<br />");


Response.Write(m.Do(Action.Insert, new MessageModel("第4条", DateTime.Now)));


Response.Write("<br />");


Response.Write(m.Do(Action.Delete, new MessageModel("第2条", DateTime.Now)));


Response.Write("<br />");


Response.Write(m.Do(Action.Insert, new MessageModel("第5条", DateTime.Now)));


Response.Write("<br />");


Response.Write(m.Do(Action.Delete, new MessageModel("第3条", DateTime.Now)));


Response.Write("<br />");


Response.Write(m.Do(Action.Insert, new MessageModel("第6条", DateTime.Now)));


Response.Write("<br />");


Response.Write(m.Do(Action.Insert, new MessageModel("第7条", DateTime.Now)));


Response.Write("<br />");


Response.Write("<br />");




Response.Write("撤销4次操作");


Response.Write("<br />");


Response.Write(m.Undo(4));


Response.Write("<br />");


Response.Write("<br />");




Response.Write("重复2次操作");


Response.Write("<br />");


Response.Write(m.Redo(2));


Response.Write("<br />");


Response.Write("<br />");




Response.Write("撤销3次操作");


Response.Write("<br />");


Response.Write(m.Undo(3));


}


}



运行结果
操作
Insert：第1条
Insert：第2条
Insert：第3条
Insert：第4条
Delete：第2条
Insert：第5条
Delete：第3条
Insert：第6条
Insert：第7条

撤销4次操作
Delete：第7条 Delete：第6条 Insert：第3条 Delete：第5条

重复2次操作
Insert：第5条 Delete：第3条

撤销3次操作
Insert：第3条 Delete：第5条 Insert：第2条

OK
[源码下载]