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状态模式（State Pattern）

发布时间：2020-12-12 14:37:42 所属栏目：MsSql教程来源：网络整理

导读：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。 M

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;

?System.Collections.Generic;

?System.Text;

namespace ?Pattern.State

{

????///?<summary>

?????Message实体类

????</summary>

????public?class?MessageModel

????{

????????

?????????构造函数

????????</summary><param?name="msg">Message内容</param>

????????<param?name="pt">Message发布时间</param>

?????????MessageModel(string?msg,?DateTime?pt)

????????{

????????????this._message?=?msg;

????????????._publishTime??pt;

????????}

????????private?_message;

?????????Message内容

?????????Message

????????{

????????????get?{?return?_message;?}

????????????set?{?_message??value;?}

????????}?DateTime?_publishTime;

?????????Message发布时间

?????????DateTime?PublishTime

????????{

??????????????_publishTime;?}

?????????????{?_publishTime?

????}

}

AbstractMessageState

?Pattern.State

{

?????状态模式抽象类

????abstract?AbstractMessageState

????{

?????????Context类型

????????protected?Message?_message;

?????????Context类型属性

?????????Message?Message

????????{

?????????????

?????????????

?????????改变状态

????????void?StateChangeCheck();

?????????获取Message

????????<returns></returns>

?List<MessageModel>?Get();

?????????插入Message

????????<param?name="mm">Message实体对象bool?Insert(MessageModel?mm);

????}
XmlMessage

?Pattern.State

{

?????Xml方式操作Message

?????XmlMessage?:?AbstractMessageState

????{

????????<param?name="message">Context类型参数?XmlMessage(Message?message)

?????????message;

????????}

????????override?StateChangeCheck()

????????//?如果UserId是admin则变换状态为SqlMessage

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

????????????{

????????????????._message.AbstractMessageState?new?SqlMessage(._message);

????????????}

?????????Get()

????????{

????????????List?l?();

????????????l.Add(XML方式获取Message,?DateTime.Now));

?????????????l;

????????}

?????????Insert(MessageModel?mm)

?????????代码略true;

????????}
SqlMessage

?Pattern.State

?Sql方式操作Message

?????SqlMessage?:?AbstractMessageState

?????SqlMessage(Message?message)

?????????StateChangeCheck()

????????{

????????}

?????????Get()

????????SQL方式获取Message

?????????Insert(MessageModel?mm)

????????
Message

?Pattern.State

{

?????Context类

?????Message

????{

?????????类型为状态模式抽象类的私有变量

?????????AbstractMessageState?_abstractMessageState;

?????????类型为状态模式抽象类的属性

?????????AbstractMessageState?AbstractMessageState

????????{

??????????????_abstractMessageState;?}

?????????????{?_abstractMessageState????????

?????????UserId私有变量

?????????_userId;

?????????UserId

?????????UserId

????????{

??????????????_userId;?}

?????????????{?_userId?

????????<param?name="userId">UserId?Message(?userId)

????????._userId??userId;

????????????_abstractMessageState??XmlMessage();

????????}

?????????Get()

?????????修改状态????????????_abstractMessageState.StateChangeCheck();

?????????????_abstractMessageState.Get();

????????}

?????????Insert(MessageModel?mm)

?????????_abstractMessageState.Insert(mm);

????????}

client

?System.Data;

?System.Configuration;

?System.Collections;

?System.Web;

?System.Web.Security;

?System.Web.UI;

?System.Web.UI.WebControls;

?System.Web.UI.WebControls.WebParts;

?System.Web.UI.HtmlControls;

?Pattern.State;

public ?partial? class ?State?:?System.Web.UI.Page

{

?????Page_Load(object?sender,?EventArgs?e)

????{

????????Message?m?);

????????Response.Write(m.Insert(插入

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

????????Response.Write(m.Get()[0].Message?+?m.Get()[].PublishTime.ToString());

????????Response.Write();

????????m?user);

????}
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

参考
http://www.dofactory.com/Patterns/PatternState.aspx

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