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设计模式 - Template Method Pattern(模板方法模式)
作者：
webabcd
介绍
定义一个操作中的算法的骨架，而将一些步骤延迟到子类中。Template Method使得子类可以不改变一个算法的结构即可重定义该算法的某些特定步骤。
示例
有一个Message实体类，对它的操作有Get()方法，每次Get()之前要使用ValidateUser()方法来检查当前用户是否有权限，获取数据可能在SqlServer数据库中或Xml文件里。（这里先检查用户的权限，再获取数据就是算法的骨架，获取数据延迟到子类中实现）
MessageModel
using
?System;
using
?System.Collections.Generic;
using
?System.Text;
namespace
?Pattern.TemplateMethod
{
????/**////?<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;?}
????????}
????}
}
AbstractMessageTemplate
using
?System;
using
?System.Collections.Generic;
using
?System.Text;
namespace
?Pattern.TemplateMethod
{
????/**////?<summary>
????///?模板方法抽象类
????///?</summary>
????public?abstract?class?AbstractMessageTemplate
????
{
????????/**////?<summary>
????????///?UserId
????????///?</summary>
????????protected?string?_userId;
????????/**////?<summary>
????????///?构造函数
????????///?</summary>
????????///?<param?name="userId">UserId</param>
????????public?AbstractMessageTemplate(string?userId)
????????
{
????????????this._userId?=?userId;
????????}
???????
????????/**////?<summary>
????????///?验证用户是否合法
????????///?</summary>
????????///?<returns></returns>
????????public?virtual?bool?ValidateUser()
????????
{
????????????if?(this._userId?==?"admin")
????????????
{
????????????????return?true;
????????????}
????????????else
????????????
{
????????????????return?false;
????????????}
????????}
????????/**////?<summary>
????????///?获取MessageModel列表
????????///?</summary>
????????///?<returns></returns>
????????public?abstract?List<MessageModel>?Get();
????????/**////?<summary>
????????///?模板方法：先验证用户是否合法，再获取MessageModel列表
????????///?</summary>
????????///?<returns></returns>
????????public?List<MessageModel>?TemplateMethodGet()
????????
{
????????????if?(ValidateUser())
????????????
{
????????????????return?Get();
????????????}
????????????else
????????????
{
????????????????List<MessageModel>?l?=?new?List<MessageModel>();
????????????????l.Add(new?MessageModel("无权获取",?DateTime.Now));
????????????????return?l;
????????????}
????????}
????}
}
SqlMessage
using
?System;
using
?System.Collections.Generic;
using
?System.Text;
namespace
?Pattern.TemplateMethod
{
????/**////?<summary>
????///?Sql方式操作Message
????///?</summary>
????public?class?SqlMessage?:?AbstractMessageTemplate
????
{
????????/**////?<summary>
????????///?构造函数
????????///?</summary>
????????///?<param?name="userId">UserId</param>
????????public?SqlMessage(string?userId)
????????????:?base(userId)
????????
{?
????????}
????????/**////?<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;
????????}
????}
}
XmlMessage
using
?System;
using
?System.Collections.Generic;
using
?System.Text;
namespace
?Pattern.TemplateMethod
{
????/**////?<summary>
????///?Xml方式操作Message
????///?</summary>
????public?class?XmlMessage?:?AbstractMessageTemplate
????
{
????????/**////?<summary>
????????///?构造函数
????????///?</summary>
????????///?<param?name="userId">UserId</param>
????????public?XmlMessage(string?userId)
????????????:?base(userId)
????????
{
????????}
????????/**////?<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;
????????}
????}
}
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.TemplateMethod;
public
?partial?
class
?TemplateMethod?:?System.Web.UI.Page
{
????protected?void?Page_Load(object?sender,?EventArgs?e)
????
{
????????AbstractMessageTemplate?m?=?new?XmlMessage("user");
????????Response.Write(m.TemplateMethodGet()[0].Message?+?"?"?+?m.TemplateMethodGet()[0].PublishTime.ToString());
????????Response.Write("<br?/>");
????????m?=?new?SqlMessage("admin");
????????Response.Write(m.TemplateMethodGet()[0].Message?+?"?"?+?m.TemplateMethodGet()[0].PublishTime.ToString());
????????Response.Write("<br?/>");
????}
}
运行结果
无权获取 2007-3-13 22:29:55
SQL方式获取Message 2007-3-13 22:29:55
OK
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