.NET平台依赖注入机制及IoC的设计与实现

using System;
using System.Web;
using System.Web.Caching;

namespace NGuestBook.Utility
{
/**//// <summary>
/// 辅助类，用于缓存操作
/// </summary>
public sealed class CacheAccess
{
/**//// <summary>
/// 将对象加入到缓存中
/// </summary>
/// <param name="cacheKey">缓存键</param>
/// <param name="cacheObject">缓存对象</param>
/// <param name="dependency">缓存依赖项</param>
public static void SaveToCache(string cacheKey,object cacheObject,CacheDependency dependency)
{
Cache cache = HttpRuntime.Cache;
cache.Insert(cacheKey,cacheObject,dependency);
}

/**//// <summary>
/// 从缓存中取得对象，不存在则返回null
/// </summary>
/// <param name="cacheKey">缓存键</param>
/// <returns>获取的缓存对象</returns>
public static object GetFromCache(string cacheKey)
{
Cache cache = HttpRuntime.Cache;

return cache[cacheKey];
}
}
}

using System;
using System.Configuration;
using System.Reflection;
using System.Web;
using System.Web.Caching;
using NGuestBook.Utility;

namespace NGuestBook.Factory
{
/**//// <summary>
/// 依赖注入提供者
/// 使用反射机制实现
/// </summary>
public sealed class DependencyInjector
{
/**//// <summary>
/// 取得数据访问层对象
/// 首先检查缓存中是否存在，如果不存在，则利用反射机制返回对象
/// </summary>
/// <param name="className">数据访问类名称</param>
/// <returns>数据访问层对象</returns>
public static object GetDALObject(string className)
{
/**//// <summary>
/// 取得数据访问层名称，首先检查缓存，不存在则到配置文件中读取
/// 缓存依赖项为Web.Config文件
/// </summary>
object dal = CacheAccess.GetFromCache("DAL");
if (dal == null)
{
CacheDependency fileDependency = new CacheDependency(HttpContext.Current.Server.MapPath("Web.Config"));
dal = ConfigurationManager.AppSettings["DAL"];
CacheAccess.SaveToCache("DAL",dal,fileDependency);
}

/**//// <summary>
/// 取得数据访问层对象
/// </summary>
string dalName = (string)dal;
string fullClassName = dalName + "." + className;
object dalObject = CacheAccess.GetFromCache(className);
if (dalObject == null)
{
CacheDependency fileDependency = new CacheDependency(HttpContext.Current.Server.MapPath("Web.Config"));
dalObject = Assembly.Load(dalName).CreateInstance(fullClassName);
CacheAccess.SaveToCache(className,dalObject,fileDependency);
}

return dalObject;
}

/**//// <summary>
/// 取得业务逻辑层对象
/// 首先检查缓存中是否存在，如果不存在，则利用反射机制返回对象
/// </summary>
/// <param name="className">业务逻辑类名称</param>
/// <returns>业务逻辑层对象</returns>
public static object GetBLLObject(string className)
{
/**//// <summary>
/// 取得业务逻辑层名称，首先检查缓存，不存在则到配置文件中读取
/// 缓存依赖项为Web.Config文件
/// </summary>
object bll = CacheAccess.GetFromCache("BLL");
if (bll == null)
{
CacheDependency fileDependency = new CacheDependency(HttpContext.Current.Server.MapPath("Web.Config"));
bll = ConfigurationManager.AppSettings["BLL"];
CacheAccess.SaveToCache("BLL",bll,fileDependency);
}

/**//// <summary>
/// 取得业务逻辑层对象
/// </summary>
string bllName = (string)bll;
string fullClassName = bllName + "." + className;
object bllObject = CacheAccess.GetFromCache(className);
if (bllObject == null)
{
CacheDependency fileDependency = new CacheDependency(HttpContext.Current.Server.MapPath("Web.Config"));
bllObject = Assembly.Load(bllName).CreateInstance(fullClassName);
CacheAccess.SaveToCache(className,bllObject,fileDependency);
}

return bllObject;
}
}
}

using System;
using NGuestBook.IDAL;

namespace NGuestBook.Factory
{
/**//// <summary>
/// 数据访问层工厂，用于获取相应的数据访问层对象
/// 使用Abstract Factory设计模式+Facace设计模式+反射机制+缓存机制设计
/// </summary>
public sealed class DALFactory
{
/**//// <summary>
/// 获取管理员数据访问层对象
/// </summary>
/// <returns>管理员数据访问层对象</returns>
public static IAdminDAL CreateAdminDAL()
{
return (IAdminDAL)DependencyInjector.GetDALObject("AdminDAL");
}
/**//// <summary>
/// 获取留言数据访问层对象
/// </summary>
/// <returns>留言数据访问层对象</returns>
public static IMessageDAL CreateMessageDAL()
{
return (IMessageDAL)DependencyInjector.GetDALObject("MessageDAL");
}

/**//// <summary>
/// 获取评论数据访问层对象
/// </summary>
/// <returns>评论数据访问层对象</returns>
public static ICommentDAL CreateCommentDAL()
{
return (ICommentDAL)DependencyInjector.GetDALObject("CommentDAL");
}
}
}

using System;
using NGuestBook.IBLL;

namespace NGuestBook.Factory
{
/**//// <summary>
/// 业务逻辑层工厂，用于获取相应的业务逻辑层对象
/// 使用Abstract Factory设计模式+Facace设计模式+反射机制+缓存机制设计
/// </summary>
public sealed class BLLFactory
{
/**//// <summary>
/// 获取管理员业务逻辑层对象
/// </summary>
/// <returns>管理员业务逻辑层对象</returns>
public static IAdminBLL CreateAdminBLL()
{
return (IAdminBLL)DependencyInjector.GetBLLObject("AdminBLL");
}

/**//// <summary>
/// 获取留言业务逻辑层对象
/// </summary>
/// <returns>留言业务逻辑层对象</returns>
public static IMessageBLL CreateMessageBLL()
{
return (IMessageBLL)DependencyInjector.GetBLLObject("MessageBLL");
}

/**//// <summary> /// 获取评论业务逻辑层对象 /// </summary> /// <returns>评论业务逻辑层对象</returns> public static ICommentBLL CreateCommentBLL() { return (ICommentBLL)DependencyInjector.GetBLLObject("CommentBLL"); } }}