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设计模式 - State Pattern(状态模式)??
[源码下载]
设计模式 - State Pattern(状态模式)
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]
（编辑：李大同）
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