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

Posted on 2007-01-22 08:26  webabcd  阅读(...)  评论(...编辑  收藏
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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");
        }

    }

}


MessageProviderCollection
using System.Configuration.Provider;
using System;

namespace Pattern.Provider
{
    
/// <summary>
    
/// Message的Provider集合类
    
/// </summary>

    public class MessageProviderCollection : ProviderCollection
    
{
        
/// <summary>
        
/// 向集合中添加提供程序。
        
/// </summary>
        
/// <param name="provider">要添加的提供程序。</param>

        public override void Add(ProviderBase provider)
        
{
            
if (provider == null)
                
throw new ArgumentNullException("provider参数不能为null");

            
if (!(provider is MessageProvider))
                
throw new ArgumentException("provider参数类型必须是MessageProvider.");

            
base.Add(provider);
        }

    }

}


MessageProviderConfigurationSection
using System.Configuration;

namespace Pattern.Provider
{
    
/// <summary>
    
/// Message的Provider的配置
    
/// </summary>

    public class MessageProviderConfigurationSection : ConfigurationSection
    
{
        
private readonly ConfigurationProperty _defaultProvider;
        
private readonly ConfigurationProperty _providers;
        
private ConfigurationPropertyCollection _properties;
        
        
/// <summary>
        
/// 构造函数
        
/// </summary>

        public MessageProviderConfigurationSection()
        
{
            _defaultProvider 
= new ConfigurationProperty("defaultProvider"typeof(string), null);
            _providers 
= new ConfigurationProperty("providers"typeof(ProviderSettingsCollection), null);
            _properties 
= new ConfigurationPropertyCollection();

            _properties.Add(_providers);
            _properties.Add(_defaultProvider);
        }


        
/// <summary>
        
/// Message的默认的Provider
        
/// </summary>

        [ConfigurationProperty("defaultProvider")]
        
public string DefaultProvider
        
{
            
get return (string)base[_defaultProvider]; }
            
set base[_defaultProvider] = value; }
        }


        
/// <summary>
        
/// Message的所有的Provider集合
        
/// </summary>

        [ConfigurationProperty("providers", DefaultValue = "SqlMessageProvider")]
        [StringValidator(MinLength 
= 1)]
        
public ProviderSettingsCollection Providers
        
{
            
get return (ProviderSettingsCollection)base[_providers]; }
        }


        
/// <summary>
        
/// Message的Provider的属性集合
        
/// </summary>

        protected override ConfigurationPropertyCollection Properties
        
{
            
get return _properties; }
        }

    }

}


Message
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Web.Configuration;

namespace Pattern.Provider
{
    
/// <summary>
    
/// 暴露给客户端用的Message的类(Context)
    
/// </summary>

    public class Message
    
{
        
private static bool m_isInitialized = false;
        
private static MessageProviderCollection _providers = null;
        
private static MessageProvider _provider = null;

        
/// <summary>
        
/// 静态构造函数,初始化
        
/// </summary>

        static Message()
        
{
            Initialize();
        }


        
/// <summary>
        
/// 插入信息
        
/// </summary>
        
/// <param name="mm">Message实体对象</param>
        
/// <returns></returns>

        public static bool Insert(MessageModel mm)
        
{
            
return _provider.Insert(mm);
        }


        
/// <summary>
        
/// 获取信息
        
/// </summary>
        
/// <returns></returns>

        public static List<MessageModel> Get()
        
{
            
return _provider.Get();
        }


        
private static void Initialize()
        
{
            
try
            
{
                MessageProviderConfigurationSection messageConfig 
= null;

                
if (!m_isInitialized)
                
{

                    
// 找到配置文件中“MessageProvider”节点
                    messageConfig = (MessageProviderConfigurationSection)ConfigurationManager.GetSection("MessageProvider");

                    
if (messageConfig == null)
                        
throw new ConfigurationErrorsException("在配置文件中没找到“MessageProvider”节点");

                    _providers 
= new MessageProviderCollection();

                    
// 使用System.Web.Configuration.ProvidersHelper类调用每个Provider的Initialize()方法
                    ProvidersHelper.InstantiateProviders(messageConfig.Providers, _providers, typeof(MessageProvider));

                    
// 所用的Provider为配置中默认的Provider
                    _provider = _providers[messageConfig.DefaultProvider] as MessageProvider;

                    m_isInitialized 
= true;

                }

            }

            
catch (Exception ex)
            
{
                
string msg = ex.Message;
                
throw new Exception(msg);
            }

        }


        
private static MessageProvider Provider
        
{
            
get
            
{
                
return _provider;
            }

        }


        
private static MessageProviderCollection Providers
        
{
            
get
            
{
                
return _providers;
            }

        }

    }

}



Web.config
<?xml version="1.0" encoding="utf-8"?>
<configuration>
  
<configSections>
    
<section name="MessageProvider" type="Pattern.Provider.MessageProviderConfigurationSection, Pattern.Provider" />
  
</configSections>
  
<MessageProvider defaultProvider="SqlMessageProvider">
    
<providers>
      
<add name="XmlMessageProvider" type="Pattern.Provider.XmlMessageProvider, Pattern.Provider" connectionStringName="XmlConnection" />
      
<add name="SqlMessageProvider" type="Pattern.Provider.SqlMessageProvider, Pattern.Provider" connectionStringName="SqlConnection" />
    
</providers>
  
</MessageProvider>
  
<connectionStrings>
    
<add name="SqlConnection" connectionString="server=.;database=db;uid=sa;pwd=sa" />
    
<add name="XmlConnection" connectionString="XmlPath" />
  
</connectionStrings>
</configuration>

Test
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.Provider;

public partial class Provider : System.Web.UI.Page
{
    
protected void Page_Load(object sender, EventArgs e)
    
{
        Response.Write(Message.Insert(
new MessageModel("插入", DateTime.Now)));
        Response.Write(
"<br />");
        Response.Write(Message.Get()[
0].Message + " " + Message.Get()[0].PublishTime.ToString());
    }

}

运行结果
True
SQL方式,连接字符串是server=.;database=db;uid=sa;pwd=sa 2007-1-22 8:21:44


OK
[源码下载]