asp.net Forums 之HttpHandler和HttpModule
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。