简单的mvc之三：灵活的路由(上)

　　在上一篇关于管线的随笔中已经提及了管线，通过对管线的分析，我们可以得到下面几个结论：路由系统由URLRoutingModule模块实现，它订阅了PostResolvRequestCache事件；路由系统通过查阅路由并尽可能的通过RemapHandler方法，确定excuteHandler阶段执行的IHttphandler。这一篇随笔想详细谢谢路由的定义、注册和导航的具体过程。

　　路由系统的导航过程定义于URLRoutingModule，具体实现如下：

 1 public virtual void PostResolveRequestCache(HttpContextBase context)
 2 {
 3     RouteData routeData = this.RouteCollection.GetRouteData(context);
 4     if (routeData != null)
 5     {
 6         IRouteHandler routeHandler = routeData.RouteHandler;
 7         if (routeHandler == null)
 8         {
 9             throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, SR.GetString("UrlRoutingModule_NoRouteHandler"), new object[0]));
10         }
11         if (!(routeHandler is StopRoutingHandler))
12         {
13             RequestContext requestContext = new RequestContext(context, routeData);
14             context.Request.RequestContext = requestContext;
15             IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext);
16             if (httpHandler == null)
17             {
18                 throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, SR.GetString("UrlRoutingModule_NoHttpHandler"), new object[] { routeHandler.GetType() }));
19             }
20             if (httpHandler is UrlAuthFailureHandler)
21             {
22                 if (!FormsAuthenticationModule.FormsAuthRequired)
23                 {
24                     throw new HttpException(0x191, SR.GetString("Assess_Denied_Description3"));
25                 }
26                 UrlAuthorizationModule.ReportUrlAuthorizationFailure(HttpContext.Current, this);
27             }
28             else
29             {
30                 context.RemapHandler(httpHandler);
31             }
32         }
33     }
34 }
35 
36  
37 
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