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

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
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