我们先说说IHttpHandler和IHttpModule这两个接口。
微软的解释为：
IHttpHandler: 定义 ASP.NET 为使用自定义 HTTP 处理程序同步处理 HTTP Web 请求而实现的协定。
IHttpModule: 向继承类提供模块初始化和处置事件。
有点看不懂，微软的解释一向如此。
那我们来看看代码：
public interface IHttpHandler
{
bool IsReusable { get; }
void ProcessRequest(HttpContext context);
}
IsReusable获取一个值，该值指示其他请求是否可以使用 System.Web.IHttpHandler 实例。
ProcessRequest()方法是处理请求的，System.Web.HttpContext 对象，它提供对用于为 HTTP 请求提供服务的内部服务器对象（如 Request、Response、Session 和 Server）的引用。
public interface IHttpModule
{
void Dispose();
void Init(HttpApplication context);
}
Dispose()方法用于释放资源。
Init()方法初始化这个HttpApplication,你可以在这时注册各类事件，如：Application_BeginRequest，Application_AuthenticateRequest，Application_OnError等。
那IHttpHandler与IHttpModule有什么区别呢：
1.先后次序.先IHttpModule,后IHttpHandler. 注:Module要看你响应了哪个事件，一些事件是在Handler之前运行的，一些是在Handler之后运行的
2.对请求的处理上:
IHttpModule是属于大小通吃类型,无论客户端请求的是什么文件,都会调用到它;例如aspx,rar,html的请求.
IHttpHandler则属于挑食类型,只有ASP.net注册过的文件类型(例如aspx,asmx等等)才会轮到调用它.
3.IHttpHandler按照你的请求生成响应的内容，IHttpModule对请求进行预处理，如验证、修改、过滤等等，同时也可以对响应进行处理 HttpHandler是HTTP请求的处理中心，真正地对客户端请求的服务器页面做出编译和执行，并将处理过后的信息附加在HTTP请求信息流中再次返回到HttpModule中。
HttpHandler与HttpModule不同，一旦定义了自己的HttpHandler类，那么它对系统的HttpHandler的关系将是“覆盖”关系。
接下来，我们再来看看ANF中的IHttpModule和IHttpHandler。
ForumsHttpModule类是ANF中自定义的HttpModule，它位于AspNetForums命名空间下。
在这个HttpModule中，自定义了
代码
/// <summary>
/// 应用程序初始化
/// </summary>
/// <param name="application"></param>
public void Init(HttpApplication application)
{
// Wire-up application events
//
application.BeginRequest += new EventHandler(this.Application_BeginRequest);
application.AuthenticateRequest += new EventHandler(Application_AuthenticateRequest);
application.Error += new EventHandler(this.Application_OnError);
application.AuthorizeRequest += new EventHandler(this.Application_AuthorizeRequest);
#if DEBUG
application.ReleaseRequestState += new EventHandler(this.Application_ReleaseRequestState);
#endif
ForumConfiguration forumConfig = ForumConfiguration.GetConfig();
if (forumConfig != null
&& forumConfig.IsBackgroundThreadingDisabled == false)
{
if (emailTimer == null)
emailTimer = new Timer(new TimerCallback(ScheduledWorkCallbackEmailInterval), application.Context, EmailInterval, EmailInterval);
if (forumConfig.IsIndexingDisabled == false
&& statsTimer == null)
{
statsTimer = new Timer(new TimerCallback(ScheduledWorkCallbackStatsInterval), application.Context, StatsInterval, StatsInterval);
}
}
}
应用程序错误处理 Application_OnError
代码
private void Application_OnError(Object source, EventArgs e)
{
ForumConfiguration forumConfig = ForumConfiguration.GetConfig();
string defaultLanguage = forumConfig.DefaultLanguage;
HttpApplication application = (HttpApplication) source;
HttpContext context = application.Context;
ForumException forumException;
string html;
StreamReader reader;
// 增加异常信息不同级别显示--开始
// 如果为管理员,显示异常详细信息 by venjiang 2004-11-3
// 发布时注释此代码
// if(Users.GetUser().IsAdministrator)
// {
// context.Response.Write(context.Server.GetLastError().Message);
// return;
// }
// 增加异常信息不同级别显示--结束
if (context.Server.GetLastError().GetBaseException() is ForumException)
{
forumException = (ForumException) context.Server.GetLastError().GetBaseException();
switch (forumException.ExceptionType)
{
case ForumExceptionType.DataProvider:
// We can't connect to the data store
//
reader = new StreamReader(context.Server.MapPath("~/Languages/" + defaultLanguage + "/errors/DataStoreUnavailable.htm"));
html = reader.ReadToEnd();
reader.Close();
html = html.Replace("[DATASTOREEXCEPTION]", forumException.Message);
context.Response.Write(html);
context.Response.End();
break;
case ForumExceptionType.UserInvalidCredentials:
forumException.Log();
break;
case ForumExceptionType.AccessDenied:
forumException.Log();
break;
case ForumExceptionType.AdministrationAccessDenied:
forumException.Log();
break;
case ForumExceptionType.ModerateAccessDenied:
forumException.Log();
break;
case ForumExceptionType.PostDeleteAccessDenied:
forumException.Log();
break;
case ForumExceptionType.PostProblem:
forumException.Log();
break;
case ForumExceptionType.UserAccountBanned:
forumException.Log();
break;
// LN 6/9/04: New exception added
case ForumExceptionType.ResourceNotFound:
//context.Response.Write(context.Server.GetLastError().Message);
forumException.Log();
break;
case ForumExceptionType.UserUnknownLoginError:
forumException.Log();
break;
}
}
else
{
forumException = new ForumException(ForumExceptionType.UnknownError, context.Server.GetLastError().Message, context.Server.GetLastError());
forumException.Log();
}
if (forumException.ExceptionType == ForumExceptionType.UnknownError)
{
if ((context.IsCustomErrorEnabled) && (!context.Request.Url.IsLoopback))
ForumContext.RedirectToMessage(context, forumException);
}
else
{
//context.Response.Write(context.Server.GetLastError().Message);
ForumContext.RedirectToMessage(context, forumException);
}
}
当安全模块已建立用户标识时发生 Application_AuthenticateRequest
代码
private void Application_AuthenticateRequest(Object source, EventArgs e)
{
HttpContext context = HttpContext.Current;
Provider p = null;
ExtensionModule module = null;
// Only continue if we have a valid context
//
if ((context == null) || (context.User == null))
return;
try
{
// Logic to handle various authentication types
//
switch (context.User.Identity.AuthenticationType.ToLower())
{
// Microsoft passport
case "passport":
p = (Provider) ForumConfiguration.GetConfig().Extensions["PassportAuthentication"];
module = ExtensionModule.Instance(p);
module.ProcessRequest();
break;
// Windows
case "negotiate":
p = (Provider) ForumConfiguration.GetConfig().Extensions["WindowsAuthentication"];
module = ExtensionModule.Instance(p);
module.ProcessRequest();
break;
default:
ForumContext.Current.UserName = context.User.Identity.Name;
break;
}
}
catch (Exception ex)
{
ForumException forumEx = new ForumException(ForumExceptionType.UnknownError, "Error in AuthenticateRequest", ex);
forumEx.Log();
throw forumEx;
}
// 获取用户角色
Roles roles = new Roles();
roles.GetUserRoles();
}
验证用户授权 Application_AuthorizeRequest
代码
private void Application_AuthorizeRequest(Object source, EventArgs e)
{
HttpApplication application = (HttpApplication) source;
HttpContext context = application.Context;
// Track anonymous users
//
Users.TrackAnonymousUsers();
// Do we need to force the user to login?
//
if (Users.GetUser().ForceLogin)
{
Moderate.ToggleUserSettings(ModerateUserSetting.ToggleForceLogin, Users.GetUser(), 0);
context.Response.Redirect(Globals.GetSiteUrls().Logout, true);
}
}
响应应用程序请求开始事件 Application_BeginRequest
代码
private void Application_BeginRequest(Object source, EventArgs e)
{
if (HttpContext.Current.Request.Path.IndexOf('\\') >= 0 ||
Path.GetFullPath(HttpContext.Current.Request.PhysicalPath) != HttpContext.Current.Request.PhysicalPath)
{
throw new HttpException(404, "not found");
}
//2005-6-25
//阻止IP访问
//
try
{
HttpApplication application = (HttpApplication) source;
HttpContext context = application.Context;
if (application == null
|| context == null)
return;
// Url Rewriting
string newPath = null;
string path = context.Request.Path;
string query = context.Request.Url.Query;
bool isReWritten = RewriteUrl(path, query, out newPath);
if (isReWritten && newPath != null)
context.RewritePath(newPath);
ForumContext frmContext = CreateForumContext(context);
frmContext.CurrentUrl = context.Request.RawUrl.ToString();
// 2005/04/07
//safe to set url rewrite data;
if (isReWritten && newPath != null)
{
frmContext.IsUrlReWritten = true;
}
// Capture any pingback information
//
CaptureForumPingback();
// Are the forums disabled?
//
if ((Globals.GetSiteSettings().ForumsDisabled) && (HttpContext.Current.Request.Url.Host != "localhost"))
{
ForumConfiguration forumConfig = ForumConfiguration.GetConfig();
string defaultLanguage = forumConfig.DefaultLanguage;
// Forums is disabled
//
StreamReader reader = new StreamReader(context.Server.MapPath("~/Languages/" + defaultLanguage + "/errors/ForumsDisabled.htm"));
string html = reader.ReadToEnd();
reader.Close();
context.Response.Write(html);
context.Response.End();
}
}
catch (Exception ex)
{
ForumException forumEx = new ForumException(ForumExceptionType.UnknownError, "Unknown error in BeginRequest", ex);
forumEx.Log();
}
if (HttpContext.Current.Request.Path.ToLower().IndexOf("msgs/default") < 0)
{
if (BlockedIpAddresses.AddressIsBlocked(Globals.IPAddress))
throw new ForumException(ForumExceptionType.BlockedIpAddress);
}
}
等事件。
在Web.Config文件中配置
<!-- 指定应用程序HttpModule -->
<httpModules>
<add name="AspNetForums" type="AspNetForums.ForumsHttpModule, AspNetForums.Components" />
</httpModules>
AvatarHttpHandler类是ANF中的自定义HttpHandler,它位于AspNetForums.Components.HttpHandler命名空间下。
这个HttpHandler主要用于处理用户头像的处理。
代码
public void ProcessRequest(HttpContext context)
{
try
{
Avatar userAvatar = Resources.GetAvatar(int.Parse(context.Request.QueryString["UserID"]));
context.Response.ContentType = userAvatar.ContentType;
context.Response.OutputStream.Write(userAvatar.Content, 0, userAvatar.Length);
context.Response.Cache.SetCacheability(HttpCacheability.Public);
// Terry Denham 7/16/2004
// changing default cache for avatars from 1 day to 30 minutes
context.Response.Cache.SetExpires(DateTime.Now.AddMinutes(10));
context.Response.Cache.SetAllowResponseInBrowserHistory(true);
context.Response.Cache.SetValidUntilExpires(true);
context.Response.Cache.VaryByParams["UserID"] = true;
}
catch
{
}
}
在Web.Config文件中的配置。
代码
<!-- 指定应用程序HttpHandlers -->
<httpHandlers>
<add verb="GET" path="avatar.aspx" type="AspNetForums.Components.HttpHandler.AvatarHttpHandler, AspNetForums.Components" />
<add verb="GET" path="vcard.aspx" type="AspNetForums.Components.HttpHandler.VCardHttpHandler, AspNetForums.Components" />
注： 本文引用了网络上的一些资料。