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乐在其中设计模式(C#) - 外观模式(Facade Pattern)


作者:webabcd


介绍
为子系统中的一组接口提供一个一致的界面,Facade模式定义了一个高层接口,这个接口使得这一子系统更加容易使用。


示例
有一个Message实体类,某对象对它的操作有Get()方法,另外还有一个对象有一个Validate()方法来判断用户是否有权限。现在提供一个高层接口来封装这两个方法。
 

MessageModel
using System;
using System.Collections.Generic;
using System.Text;

namespace Pattern.Facade
{
        /// <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; }
                }
        }
}
 
User
using System;
using System.Collections.Generic;
using System.Text;

namespace Pattern.Facade
{
        /// <summary>
        /// 用户相关类
        /// </summary>
        public class User
        {
                /// <summary>
                /// 验证用户是否合法
                /// </summary>
                /// <param name="userId">UserId</param>
                /// <returns></returns>
                public bool Validate(string userId)
                {
                        if (userId == "admin")
                        {
                                return true;
                        }
                        else
                        {
                                return false;
                        }
                }
        }
}
 
SqlMessage
using System;
using System.Collections.Generic;
using System.Text;

namespace Pattern.Facade
{
        /// <summary>
        /// Sql方式操作Message
        /// </summary>
        public class SqlMessage
        {
                /// <summary>
                /// 获取Message
                /// </summary>
                /// <returns></returns>
                public List<MessageModel> Get()
                {
                        List<MessageModel> l = new List<MessageModel>();
                        l.Add(new MessageModel("SQL方式获取Message", DateTime.Now));

                        return l;
                }
        }
}
 
Message
using System;
using System.Collections.Generic;
using System.Text;

namespace Pattern.Facade
{
        /// <summary>
        /// Facade类
        /// </summary>
        public class Message
        {
                private string _userId = "";

                /// <summary>
                /// 构造函数
                /// </summary>
                /// <param name="userId">UserId</param>
                public Message(string userId)
                {
                        this._userId = userId;
                }

                /// <summary>
                /// 获取Message
                /// 首先使用User类的Validate()方法验证用户是否合法
                /// 然后使用SqlMessage类的Get()方法获取Message
                /// </summary>
                /// <returns></returns>
                public List<MessageModel> Get()
                {
                        User u = new User();
                        SqlMessage m = new SqlMessage();

                        if (u.Validate(_userId))
                        {
                                return m.Get();
                        }
                        else
                        {
                                List<MessageModel> l = new List<MessageModel>();
                                l.Add(new MessageModel("无权获取", 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.Facade;

public partial class Facade : System.Web.UI.Page
{
        protected void Page_Load(object sender, EventArgs e)
        {
                Message m = new Message("user");
                Response.Write(m.Get()[0].Message + " " + m.Get()[0].PublishTime.ToString());
                Response.Write("<br />");

                m = new Message("admin");
                Response.Write(m.Get()[0].Message + " " + m.Get()[0].PublishTime.ToString());
                Response.Write("<br />");
        }
}
 
 
运行结果
无权获取 2007-3-20 22:16:50
SQL方式获取Message 2007-3-20 22:16:50


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


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