乐在其中设计模式(C#) - 提供者模式(Provider Pattern)

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乐在其中设计模式(C#) - 提供者模式(Provider Pattern)

作者： webabcd


介绍
为一个API进行定义和实现的分离。


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。根据配置文件中的配置来决定数据持久化方案是使用SqlServer数据库还是Xml文件。

 

MessageModel

using System; 
 
namespace Pattern.Provider 
{ 
         /// <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; } 
                } 
        } 
}

 

MessageProvider

using System.Configuration.Provider; 
using System.Collections.Generic; 
 
namespace Pattern.Provider 
{ 
         /// <summary> 
         /// 操作Message抽象类 
         /// </summary> 
         public  abstract  class MessageProvider : ProviderBase 
        { 
                 /// <summary> 
                 /// 插入Message 
                 /// </summary> 
                 /// <param name="mm">Message实体对象</param> 
                 /// <returns></returns> 
                 public  abstract  bool Insert(MessageModel mm); 
 
                 /// <summary> 
                 /// 获得Message 
                 /// </summary> 
                 /// <returns></returns> 
                 public  abstract List<MessageModel> Get(); 
        } 
}

 

SqlMessageProvider

using System; 
using System.Collections.Specialized; 
using System.Collections.Generic; 
 
using System.Configuration.Provider; 
using System.Configuration; 
 
namespace Pattern.Provider 
{ 
         /// <summary> 
         /// Sql方式操作Message 
         /// </summary> 
         public  class SqlMessageProvider : MessageProvider 
        { 
                 private  string _connectionString; 
 
                 /// <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; 
                } 
 
                 /// <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，连接字符串是" +  this._connectionString, DateTime.Now)); 
 
                         return l; 
                } 
 
                 /// <summary> 
                 /// 初始化提供程序。 
                 /// </summary> 
                 /// <param name="name">该提供程序的友好名称。</param> 
                 /// <param name="config">名称/值对的集合，表示在配置中为该提供程序指定的、提供程序特定的属性。</param> 
                 public  override  void Initialize( string name, NameValueCollection config) 
                { 
                         if ( string.IsNullOrEmpty(name)) 
                                name =  "MessageProvider"; 
 
                         if ( null == config) 
                                 throw  new ArgumentException( "config参数不能为null"); 
 
                         if ( string.IsNullOrEmpty(config[ "description"])) 
                        { 
                                config.Remove( "description"); 
                                config.Add( "description",  "SqlServer操作Message"); 
                        } 
 
                         base.Initialize(name, config); 
 
                         string temp = config[ "connectionStringName"]; 
                         if (temp ==  null || temp.Length < 1) 
                                 throw  new ProviderException( "connectionStringName属性缺少或为空"); 
 
                        _connectionString = ConfigurationManager.ConnectionStrings[temp].ConnectionString; 
                         if (_connectionString ==  null || _connectionString.Length < 1) 
                        { 
                                 throw  new ProviderException( "没找到'" + temp +  "'所指的连接字符串，或所指连接字符串为空"); 
                        } 
 
                        config.Remove( "connectionStringName"); 
                } 
        } 
}

 

XmlMessageProvider

using System; 
using System.Collections.Specialized; 
using System.Collections.Generic; 
 
using System.Configuration.Provider; 
using System.Configuration; 
 
namespace Pattern.Provider 
{ 
         /// <summary> 
         /// Xmll方式操作Message 
         /// </summary> 
         public  class XmlMessageProvider : MessageProvider 
        { 
                 private  string _connectionString; 
 
                 /// <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; 
                } 
 
                 /// <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，连接字符串是" +  this._connectionString, DateTime.Now)); 
 
                         return l; 
                } 
 
                 /// <summary> 
                 /// 初始化提供程序。 
                 /// </summary> 
                 /// <param name="name">该提供程序的友好名称。</param> 
                 /// <param name="config">名称/值对的集合，表示在配置中为该提供程序指定的、提供程序特定的属性。</param> 
                 public  override  void Initialize( string name, NameValueCollection config) 
                { 
                         if ( string.IsNullOrEmpty(name)) 
                                name =  "MessageProvider"; 
 
                         if ( null == config) 
                                 throw  new ArgumentException( "config参数不能为null"); 
 
                         if ( string.IsNullOrEmpty(config[ "description"])) 
                        { 
                                config.Remove( "description"); 
                                config.Add( "description",  "XML操作Message"); 
                        } 
 
                         base.Initialize(name, config); 
 
                         string temp = config[ "connectionStringName"]; 
                         if (temp ==  null || temp.Length < 1) 
                                 throw  new ProviderException( "connectionStringName属性缺少或为空"); 
 
                        _connectionString = ConfigurationManager.ConnectionStrings[temp].ConnectionString; 
                         if (_connectionString ==  null || _connectionString.Length < 1) 
                        { 
                                 throw  new ProviderException( "没找到'" + temp +  "'所指的连接字符串，或所指连接字符串为空"); 
                        } 
 
                        config.Remove( "connectionStringName"); 
                } 
        } 
}

 

未完待续>>

 

 

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     本文转自webabcd 51CTO博客，原文链接：http://blog.51cto.com/webabcd/344596，如需转载请自行联系原作者