在写这篇随笔之前，其实网上早已有高手分析了.text的urlrewrite的实现（点击
这里查看全文），问题是作为一个初学者的我，看了以后，感觉没有切中要害。所以，产生了写这篇dd的冲动。
从头说起，.text是通过httpModules和httpHandlers来实现urlrewrite的，看看web.config中的配置
1
<httpHandlers> 2 <!-- Can not see to load asmx like .aspx, since we will grap all requests later, make sure these are processed by their default factory --> 3 <add verb="*" path="*.asmx" type="System.Web.Services.Protocols.WebServiceHandlerFactory, System.Web.Services, Version=1.0.5000.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"
4 validate="false" /> 5 <!--Since we are grabbing all requests after this, make sure Error.aspx does not rely on .Text --> 6 <add verb="*" path="Error.aspx" type="System.Web.UI.PageHandlerFactory" /> 7 <!--This will process any ext mapped to aspnet_isapi.dll --> 8 <add verb="*" path="*" type="Dottext.Common.UrlManager.UrlReWriteHandlerFactory,Dottext.Common" /> 9 </httpHandlers> 10 <httpModules> 11 <add name="UrlReWriteModule" type="Dottext.Common.UrlManager.UrlReWriteModule, Dottext.Common" /> 12 <add name="EventHttpModule" type="Dottext.Framework.ScheduledEvents.EventHttpModule, Dottext.Framework" /> 13 <!--<add name="MsftBlogsHttpModule" type= "AspNetWeb.MsftBlogsHttpModule, MsftBlogsHttpModule" />--> 14 </httpModules> 15
看看第11行，配置了
Dottext.Common.UrlManager.UrlReWriteModule这个httpModule，很显然，从名字来看，它就是实现urlrewrite功能的httpmodule，去看看它的源代码
1 static UrlReWriteModule()
2
{
3
regexPath = new Regex(@"^/?(\w|-|_)+\.aspx$",RegexOptions.IgnoreCase|RegexOptions.Compiled);
4 regexApplication = new Regex(HttpContext.Current.Request.ApplicationPath,RegexOptions.IgnoreCase|RegexOptions.Compiled);
5
} 6 7 private void context_BeginRequest(
object sender, EventArgs e)
8 {
9 if(ConfigProvider.Instance().IsAggregateSite)
10
{
11 HttpContext context = ((HttpApplication)sender).Context;
12
13 string path = context.Request.Path.ToLower();
14 int iExtraStuff = path.IndexOf(".aspx");
15 if(iExtraStuff > -1 || path.IndexOf(".") == -1)
16 {
17 if(iExtraStuff > -1)
18 {
19 path = path.Remove(iExtraStuff+5,path.Length - (iExtraStuff+5));
20
}
21
22 path = regexApplication.Replace(path,string.Empty,1,0);
23
24 if(path == "" || path == "/" || regexPath.IsMatch(path))
25 {
26 UrlHelper.SetEnableUrlReWriting(context,false);
27 }
28
29 }
30 else if(context.Request.Path.ToLower().IndexOf("services") > 0 && context.Request.Path.ToLower().IndexOf(".asmx") > 0 )
31 {
32 if(AlllowService(context))
33 {
34 if(context.Request.RequestType!="POST")
35 {
36 string regexstr=@"/\w+/services/";
37 string url=Regex.Replace(context.Request.RawUrl,regexstr,"/services/",RegexOptions.IgnoreCase);
38 context.RewritePath(url);
39 }
40 //string fileName =context.Request; //System.IO.Path.GetFileName(context.Request.Path);
41 //context.RewritePath("~/Services/" + fileName);
42 }
43 else
44 {
45 context.Response.Clear();
46 context.Response.End();
47 }
48 }
49
50 }
51 } 52
代码有点长，不过没关系，结构还是很清晰的。用户发出的url请求，在context_BeginRequest中进行了第一次过滤，这个函数把url做了一下归整，判断来自用户的请求是 应用程序根目录下的.aspx文件，如果是则不进行urlrewrite（由UrlHelper.SetEnableUrlReWriting这个函数进行设置）。什么？看不懂regexPath =
new Regex(@"^/?(\w|-|_)＋\.aspx$",……); 这句话？建议你去看一下正则表达式，这里的意思是指，需要匹配的字符串所对应的文件是否在根目录下，举例来说，
/contact.aspx
default.aspx
匹配，而
/oop80/default.aspx
则不匹配，
总而言之，context_BeginRequest函数把对根目录下.aspx文件的请求，以及webservice，设置成不需要进行urlrewrite，其余的，则需要进行下一步的处理，在什么地方处理呢，我们来看看web.config中的配置，第8行，很清晰的告诉我们，在
Dottext.Common.UrlManager.UrlReWriteHandlerFactory中，会对用户的请求做进一步分析和处理。 来看看源代码
1public class UrlReWriteHandlerFactory: IHttpHandlerFactory
2 {
3 public UrlReWriteHandlerFactory(){} //Nothing to do in the cnstr
4
5 protected virtual HttpHandler[] GetHttpHandlers(HttpContext context)
6 {
7 return HandlerConfiguration.Instance().HttpHandlers;
8 }
9
10 /// <summary>
11 /// Implementation of IHttpHandlerFactory. By default, it will load an array of HttpHanlder (Dottext.UrlManager.HttpHandler) from
12 /// the blog.config. This can be changed, by overrideing the GetHttpHandlers(HttpContext context) method.
13 /// </summary>
14 /// <param name="context">Current HttpContext</param>
15 /// <param name="requestType">Request Type (Passed along to other IHttpHandlerFactory's)</param>
16 /// <param name="url">The current requested url. (Passed along to other IHttpHandlerFactory's)</param>
17 /// <param name="path">The physical path of the current request. Is not gaurenteed to exist (Passed along to other IHttpHandlerFactory's)</param>
18 /// <returns>
19 /// Returns an Instance of IHttpHandler either by loading an instance of IHttpHandler or by returning an other
20 /// IHttpHandlerFactory.GetHanlder(HttpContext context, string requestType, string url, string path) method
21 /// </returns>
22 public virtual IHttpHandler GetHandler(HttpContext context, string requestType, string url, string path)
23 {
24 //Get the Handlers to process. By defualt, we grab them from the blog.config
25 //Dottext.Framework.Logger.LogManager.Log("url",context.Request.Path);
26 HttpHandler[] items = GetHttpHandlers(context);
27 //Dottext.Framework.Logger.LogManager.Log("path",Dottext.Framework.Util.Globals.RemoveAppFromPath(context.Request.Path,context.Request.ApplicationPath));
28 //Do we have any?
29 if(items != null)
30 {
31 int count = items.Length;
32
33 for(int i = 0; i<count; i++)
34 {
35 //We should use our own cached Regex. This should limit the number of Regex's created
36 //and allows us to take advantage of RegexOptons.Compiled
37
38 if(items[i].IsMatch(Dottext.Framework.Util.Globals.RemoveAppFromPath(context.Request.Path,context.Request.ApplicationPath)))
39 {
40 //throw new Exception();
41 switch(items[i].HandlerType)
42 {
43 case HandlerType.Page://默认是Page
44
45 return ProccessHandlerTypePage(items[i],context,requestType,url);
46 case HandlerType.Direct:
47 HandlerConfiguration.SetControls(context,items[i].BlogControls);
48 return (IHttpHandler)items[i].Instance();
49 case HandlerType.Factory:
50 //Pass a long the request to a custom IHttpHandlerFactory
51 return ((IHttpHandlerFactory)items[i].Instance()).GetHandler(context,requestType,url,path);
52 default:
53 throw new Exception("Invalid HandlerType: Unknown");
54 }
55 }
56 }
57 }
58 //If we do not find the page, just let ASP.NET take over
59 return PageHandlerFactory.GetHandler(context,requestType,url, path);
60 }
61
62
63 private IHttpHandler ProccessHandlerTypePage(HttpHandler item, HttpContext context, string requestType, string url)
64 {
65 string pagepath = item.FullPageLocation;
66 if(pagepath == null)
67 {
68 pagepath = HandlerConfiguration.Instance().FullPageLocation;
69 }
70 HandlerConfiguration.SetControls(context,item.BlogControls);
71 IHttpHandler myhandler=PageParser.GetCompiledPageInstance(url,pagepath,context);
72 return myhandler;
73 }
74
75
76 public virtual void ReleaseHandler(IHttpHandler handler)
77 {
78
79 }
80 } 81
代码很长，但是它是实现urlrewrite的关键，我们来分析分析看。
UrlReWriteHandlerFactory实现了IHttpHandlerFactory接口，而IHttpHandlerFactory最关键的地方在于GetHandler这个函数接口，所以我们从GetHandler函数入手。
首先是 HttpHandler [] items = GetHttpHandlers(context)； 通过查看GetHttpHandlers的定义，可以得知返回的其实是HandlerConfiguration中一个叫HttpHandlers的属性，它的值，是通过这么一句话来进行初始化的，return ((HandlerConfiguration)ConfigurationSettings.GetConfig("HandlerConfiguration")); 想必大家现在都明白了，HandlerConfiguration对象是通过将web.config中<HandlerConfiguration>节进行反序列化获得的，关于ConfigurationSettings.GetConfig的使用，网上已经有很多了，在这里就不重复劳动了。看看web.config中的HandlerConfiguration节
1 <HandlerConfiguration defaultPageLocation="default.aspx" type="Dottext.Common.UrlManager.HandlerConfiguration, Dottext.Common"> 2 <HttpHandlers> 3 <HttpHandler pattern="(\.config|\.asax|\.ascx|\.config|\.cs|\.vb|\.vbproj|\.asp|\.licx|\.resx|\.resources)$" type="Dottext.Framework.UrlManager.HttpForbiddenHandler, Dottext.Framework" handlerType="Direct" /> 4 <HttpHandler pattern="(\.gif|\.js|\.jpg|\.zip|\.jpeg|\.jpe|\.css|\.rar|\.xml|\.xsl)$" type="Dottext.Common.UrlManager.BlogStaticFileHandler, Dottext.Common" handlerType="Direct" /> 5 <HttpHandler pattern="/rss\.aspx$" type="Dottext.Common.Syndication.RssHandler, Dottext.Common" handlerType="Direct" /> 6 <HttpHandler pattern="/CommentsRSS\.aspx$" type="Dottext.Common.Syndication.RecentCommentsRSS, Dottext.Common" handlerType="Direct" /> 7 <HttpHandler pattern = "/RecentCommentsRSS\.aspx$" type = "Dottext.Common.Syndication.RecentCommentsRSS, Dottext.Common" handlerType = "Direct" /> 8 <HttpHandler pattern="/atom\.aspx$" type="Dottext.Common.Syndication.AtomHandler, Dottext.Common" handlerType="Direct" /> 9 <HttpHandler pattern="/comments/commentRss/\d+\.aspx$" type="Dottext.Common.Syndication.RssCommentHandler, Dottext.Common" handlerType="Direct" />10 <HttpHandler pattern="/aggbug/\d+\.aspx$" type="Dottext.Framework.Tracking.AggBugHandler, Dottext.Framework" handlerType="Direct" />11 <HttpHandler pattern="/customcss\.aspx$" type="Dottext.Web.UI.Handlers.BlogSecondaryCssHandler, Dottext.Web" handlerType="Direct" />12 <HttpHandler pattern="/category\/(\d|\w|\s)+\.aspx/rss$" type="Dottext.Common.Syndication.RssCategoryHandler, Dottext.Common" handlerType="Direct" />13 <HttpHandler pattern="/favorite\/(\d|\w|\s)+\.aspx/rss$" type="Dottext.Common.Syndication.RssLinksHandler, Dottext.Common" handlerType="Direct" />14 <HttpHandler pattern="/articles/\d+\.aspx$" controls="viewpost.ascx,Comments.ascx,AnonymousPostComment.ascx,LoginPostComment.ascx" />15 <HttpHandler pattern="/articles/\w+\.aspx$" controls="viewpost.ascx,Comments.ascx,AnonymousPostComment.ascx,LoginPostComment.ascx" />16 <HttpHandler pattern="/PreviewPost.aspx$" controls="PreviewPost.ascx" />17 <HttpHandler pattern="/archive/\d{4}/\d{2}/\d{2}/\d+\.(aspx|htm)$" controls="viewpost.ascx,Comments.ascx,AnonymousPostComment.ascx,LoginPostComment.ascx" />18 <HttpHandler pattern="/archive/\d{4}/\d{2}/\d{2}/\w+\.(aspx|htm)$" controls="viewpost.ascx,Comments.ascx,AnonymousPostComment.ascx,LoginPostComment.ascx" />19 <HttpHandler pattern="/archive/\d{4}/\d{1,2}/\d{1,2}\.aspx$" controls="ArchiveDay.ascx" />20 <HttpHandler pattern="/archive/\d{4}/\d{1,2}\.aspx$" controls="ArchiveMonth.ascx" />21 <HttpHandler pattern="/archives/\d{4}/\d{1,2}\.aspx$" controls="ArticleArchiveMonth.ascx" />22 <HttpHandler pattern="/contact\.aspx$" controls="Contact.ascx" />23 <HttpHandler pattern="/AddToFavorite\.aspx$" handlerType="Page" pageLocation="AddToFavorite.aspx" />24 <HttpHandler pattern="/BlogSearch\.aspx$" controls="BlogSearch.ascx" />25 <HttpHandler pattern="/posts/|/story/|/archive/" type="Dottext.Web.UI.Handlers.RedirectHandler,Dottext.Web" handlerType="Direct" />26 <HttpHandler pattern="/gallery\/\d+\.aspx$" controls="GalleryThumbNailViewer.ascx" />27 <HttpHandler pattern="/gallery\/image\/\d+\.aspx$" controls="ViewPicture.ascx" />28 <HttpHandler pattern="/(?:category|stories)/(\w|\s)+\.aspx$" controls="CategoryEntryList.ascx" />29 <HttpHandler pattern="/favorite/(\w|\s)+\.aspx$" controls="FavoriteList.ascx" />30 <HttpHandler pattern="/(?:admin)" type="Dottext.Web.UI.Handlers.BlogExistingPageHandler, Dottext.Web" handlerType="Factory" />31 <!--<HttpHandler pattern = "^(?:\/(\w|\s|\.(?!aspx))+((\/login\.aspx)?|(\/?))?)$" type = "Dottext.Web.UI.Handlers.BlogExistingPageHandler, Dottext.Web" handlerType = "Factory" />-->32 <!--<HttpHandler pattern = "^(?:/\w+\/(\w|\s|\.)+\/(?:admin|logout\.aspx|login\.aspx))" type = "Dottext.Web.UI.Handlers.BlogExistingPageHandler, Dottext.Web" handlerType = "Factory" />-->33 <HttpHandler pattern="/comments\/\d+\.aspx$" type="Dottext.Common.Syndication.CommentHandler, Dottext.Common" handlerType="Direct" />34 <HttpHandler pattern="/services\/trackbacks/\d+\.aspx$" type="Dottext.Framework.Tracking.TrackBackHandler, Dottext.Framework" handlerType="Direct" />35 <HttpHandler pattern="/services\/pingback\.aspx$" type="Dottext.Framework.Tracking.PingBackService, Dottext.Framework" handlerType="Direct" />36 <HttpHandler pattern="/services\/metablogapi\.aspx$" type="Dottext.Framework.XmlRpc.MetaWeblog, Dottext.Framework" handlerType="Direct" />37 <HttpHandler pattern="/Services\/SyncHanlder\.aspx$" handlerType="Page" pageLocation="Sevices/DottextAPI.aspx" />38 <!-- 只显示文章标题列表 -->39 <!--<HttpHandler pattern="^((/default\.aspx)|(/)|(/index\.aspx))$" controls="CategoryPostsList.ascx" />-->40 <!-- 显示文章内容 -->41 <HttpHandler pattern="^((/default\.aspx)|(/)|(/index\.aspx))$" controls="PagedPosts.ascx" />42 <HttpHandler pattern="^(/posts\.aspx)$" controls="PagedPosts.ascx" />43 <!--<HttpHandler pattern = "/services/\w+.asmx$" type="System.Web.Services.Protocols.WebServiceHandlerFactory, System.Web.Services, Version=1.0.5000.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" handlerType = "Factory" />-->44 <HttpHandler pattern = "^(?:\/(\w|\s|\.(?!aspx))+((\/default\.aspx)?|(\/?))?)$" controls = "homepage.ascx"/>45 <!--<HttpHandler pattern="^(?:/\w+\/(\w|\s|\.(?!aspx))+((\/default\.aspx)?|(\/?))?)$" controls="homepage.ascx" />-->46 47 </HttpHandlers>48 </HandlerConfiguration>49
其实在visual studio.net中看这段代码会更加清楚一点，这里的每一个pattern其实都会建立对应的Regex ，来对用户请求的url进行匹配，下面的代码会很详细说明这一点，我们往下看。
接下来是一个循环，循环中执行这么一句话
if (items[i].IsMatch(Dottext.Framework.Util.Globals.RemoveAppFromPath(context.Request.Path,context.Request.ApplicationPath))) {...}
它把web.config中每一个httphandler来匹配用户的请求，IsMatch函数中会根据pattern建立相应的Regex，并调用Regex.IsMatch函数，如果请求匹配该pattern，则调用对应的模块来进行处理。很显然，这里是实现urlrewrite的关键之处，比如，请求的是这么一个url
http://oop80.cnblogs.com/archive/2005/08/09/210550.html
那么，他就会匹配这一个handler
<HttpHandler pattern="/archive/\d{4}/\d{2}/\d{2}/\d+\.(aspx|htm)$" controls="viewpost.ascx,Comments.ascx,AnonymousPostComment.ascx,LoginPostComment.ascx" />
那么，程序就会调用 viewpost.ascx,Comments.ascx,AnonymousPostComment.ascx,LoginPostComment.ascx 来处理用户的请求，
又如，请求这么一个url
http://oop80.cnblogs.com/category/23435.aspx
匹配
<HttpHandler pattern="/(?:category|stories)/(\w|\s)+\.aspx$" controls="CategoryEntryList.ascx" />
最后程序是一个switch语句，根据handlertype的不同进行各种处理，具体就不在解释了，因为……这一段我自己也没有进行更深入一步的研究，里面还有一些细节，如SetControls的控件在什么地方载入，GetCompiledPageInstance函数的具体用法等等。不过，这些东西终归和urlrewrite没多大关系了，不在我们讨论的范围之内。
请大家多多指教，谢谢
