003. Asp.Net Routing与MVC 之一: 请求如何到达MVC

 

基础知识

本文用到的基础知识:URL、HttpModule 与 HttpHandler、IIS 的请求处理过程。

URL

HttpModule与HttpHandler

IIS7.0的请求处理过程

 

OK,现在我们来看请求如何到达MVC:

一、Asp.Net Routing 如何起作用

我们知道IIS网站的配置可以分为两个块:全局 Web.Config 和本站 Web.Config 。

Asp.Net Routing属于全局性的,所以它配置在全局Web.Config 中,我们可以在如下路径中找到:

“$\Windows\Microsoft.NET\Framework\版本号\Config\Web.config“

   1: <?xml version="1.0" encoding="utf-8"?>
   2: <!-- the root web configuration file -->
   3: <configuration>
   4:     <system.web>
   5:         <httpModules>
   6:             <add name="UrlRoutingModule-4.0" type="System.Web.Routing.UrlRoutingModule" />
   7:         </httpModules>
   8:     </system.web>
   9: </configuration>

通过在全局Web.Config中注册 System.Web.Routing.UrlRoutingModule,IIS请求处理管道接到请求后,就会加载 UrlRoutingModule类型的Init()方法。其源码入下:

   1: //UrlRoutingModule 位于 System.web.dll 文件中,利用Reflector 可以查看到其源码
   2: [TypeForwardedFrom("System.Web.Routing, Version=3.5.0.0, Culture=Neutral, PublicKeyToken=31bf3856ad364e35")]
   3: public class UrlRoutingModule : IHttpModule
   4: {
   5:     // Fields
   6:     private static readonly object _contextKey = new object();
   7:     private static readonly object _requestDataKey = new object();
   8:     private RouteCollection _routeCollection;
   9:     // Methods
  10:     protected virtual void Dispose()  {}
  11:  
  12:     //在II7处理管道中注册了的IHttpModule类型,其_Init()会被执行,以在II7处理管道中注册事件处理方法。
  13:     protected virtual void Init(HttpApplication application)
  14:     {
  15:         if (application.Context.Items[_contextKey] == null)
  16:         {
  17:             application.Context.Items[_contextKey] = _contextKey;
  18:             //这里为UrlRoutingModule 注册了一个PostResolveRequestCache 事件处理方法:OnApplicationPostResolveRequestCache().
  19:             application.PostResolveRequestCache += new EventHandler(this.OnApplicationPostResolveRequestCache);
  20:         }
  21:     }
  22:  
  23:     //发生PostResolveRequestCache 事件时,该方法被调用
  24:     private void OnApplicationPostResolveRequestCache(object sender, EventArgs e)
  25:     {
  26:         HttpContextBase context = new HttpContextWrapper(((HttpApplication) sender).Context);
  27:         //执行真正的处理 PostResolveRequestCache()
  28:         this.PostResolveRequestCache(context);
  29:     }
  30:  
  31:     [Obsolete("This method is obsolete. Override the Init method to use the PostMapRequestHandler event.")]
  32:     public virtual void PostMapRequestHandler(HttpContextBase context)
  33:     {
  34:     }
  35:  
  36:      //发生PostResolveRequestCache 事件时真正的处理
  37:     public virtual void PostResolveRequestCache(HttpContextBase context)
  38:     {
  39:         //获取路由信息(RouteCollection是其本身的属性,见this.RouteCollection)
  40:         RouteData routeData = this.RouteCollection.GetRouteData(context);
  41:         if (routeData != null)
  42:         {
  43:             //从routeData 获取 RouteHandler
  44:             // 既然routeData 内容其实来自System.Web.Routing.RouteTable.Routes
  45:             // 那么System.Web.Routing.RouteTable.Routes 里的RouteHandler到底是哪来的呢?我们需要去MVC项目里看看
  46:             IRouteHandler routeHandler = routeData.RouteHandler;
  47:             if (routeHandler == null)
  48:             {
  49:                 throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, 
  50:                                 SR.GetString("UrlRoutingModule_NoRouteHandler"), new object[0]));
  51:             }
  52:             if (!(routeHandler is StopRoutingHandler))
  53:             {
  54:                 //构建请求上下文
  55:                 RequestContext requestContext = new RequestContext(context, routeData);
  56:                 context.Request.RequestContext = requestContext;
  57:                 //调用 IRouteHandler.GetHttpHandler(),获取的IHttpHandler 类型实例 
  58:                 //IHttpHandler 类型实例 ,是由 IRouteHandler.GetHttpHandler获取的,我们去MVC源码里看
  59:                 IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext);
  60:                 if (httpHandler == null)
  61:                 {
  62:                     throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, 
  63:                                     SR.GetString("UrlRoutingModule_NoHttpHandler"), new object[] { routeHandler.GetType() }));
  64:                 }
  65:                 if (httpHandler is UrlAuthFailureHandler)
  66:                 {
  67:                     if (!FormsAuthenticationModule.FormsAuthRequired)
  68:                     {
  69:                         throw new HttpException(0x191, SR.GetString("Assess_Denied_Description3"));
  70:                     }
  71:                     UrlAuthorizationModule.ReportUrlAuthorizationFailure(HttpContext.Current, this);
  72:                 }
  73:                 else
  74:                 {
  75:                     //合适条件下,把之前将获取的IHttpHandler 类型实例 映射到IIS HTTP处理管道中
  76:                     context.RemapHandler(httpHandler);
  77:                 }
  78:             }
  79:         }
  80:     }
  81:  
  82:     void IHttpModule.Dispose()
  83:     {
  84:         this.Dispose();
  85:     }
  86:  
  87:     void IHttpModule.Init(HttpApplication application)
  88:     {
  89:         this.Init(application);
  90:     }
  91:  
  92:     // Properties
  93:     public RouteCollection RouteCollection
  94:     {
  95:         get
  96:         {
  97:             //恩,原来真实内容来自System.Web.Routing.RouteTable.Routes
  98:             if (this._routeCollection == null)
  99:             {
 100:                 this._routeCollection = RouteTable.Routes;
 101:             }
 102:             return this._routeCollection;
 103:         }
 104:         set
 105:         {
 106:             this._routeCollection = value;
 107:         }
 108:     }
 109: }

下边是PostResolveRequestCache方法里的几句核心代码:

   1: //PostResolveRequestCache方法里的核心代码:
   2:  
   3: //获取路由信息(RouteCollection是其本身的属性,见this.RouteCollection)
   4: RouteData routeData = this.RouteCollection.GetRouteData(context);
   5: //从routeData 获取 RouteHandler
   6: // 既然routeData 内容其实来自System.Web.Routing.RouteTable.Routes
   7: // 那么System.Web.Routing.RouteTable.Routes 里的RouteHandler到底是哪来的呢?我们需要去MVC项目里看看
   8: IRouteHandler routeHandler = routeData.RouteHandler;
   9:  
  10: //调用 IRouteHandler.GetHttpHandler(),获取的IHttpHandler 类型实例 
  11: //IHttpHandler 类型实例 ,是由 IRouteHandler.GetHttpHandler获取的,我们去MVC源码里看
  12: IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext);
  13:  
  14: //合适条件下,把之前将获取的IHttpHandler 类型实例 映射到IIS HTTP处理管道中
  15: context.RemapHandler(httpHandler);

 

二、MVCRouteHandler从哪来

好吧,我们需要去MVC项目里看看。众所周知,项目启动是从Global开始的,那就看看它。下边是代码:

   1: //这是一个普通MVC5 WebApp的Global.asax.cs
   2: namespace WebApplication1
   3: {
   4:     public class MvcApplication : System.Web.HttpApplication
   5:     {
   6:         protected void Application_Start()
   7:         {
   8:             AreaRegistration.RegisterAllAreas();
   9:             FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
  10:             //这里要注册路由了
  11:             RouteConfig.RegisterRoutes(RouteTable.Routes);
  12:             BundleConfig.RegisterBundles(BundleTable.Bundles);
  13:         }
  14:     }
  15:  
  16:     //为方便起见,我把项目App_Start/RouteConfig.cs内容放在一起
  17:     public class RouteConfig
  18:     {
  19:         public static void RegisterRoutes(RouteCollection routes)
  20:         {
  21:             routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
  22:             //玄机就在这了,这个MapRoute位于System.Web.Mvc.RouteCollectionExtensions
  23:             //看RouteCollectionExtensions里面做了什么
  24:             routes.MapRoute(
  25:                 name: "Default",
  26:                 url: "{controller}/{action}/{id}",
  27:                 defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
  28:             );
  29:         }
  30:     }
  31: }

下边是System.Web.Mvc.RouteCollectionExtensions.MapRoute 众多重载的最终执行者代码:

   1: //System.Web.Mvc.RouteCollectionExtensions.MapRoute 众多重载的最终执行者代码
   2: [SuppressMessage("Microsoft.Design", "CA1054:UriParametersShouldNotBeStrings", MessageId = "2#", Justification = "This is not a regular URL as it may contain special routing characters.")]
   3: public static Route MapRoute(this RouteCollection routes, string name, string url, object defaults, object constraints, string[] namespaces)
   4: {
   5:     if (routes == null)
   6:     {
   7:         throw new ArgumentNullException("routes");
   8:     }
   9:     if (url == null)
  10:     {
  11:         throw new ArgumentNullException("url");
  12:     }
  13:  
  14:     //终于找到了,“new MvcRouteHandler()”,
  15:     //直接把一个 MvcRouteHandler 实例塞到 System.Web.Routing 的初始化方法里了!
  16:     Route route = new Route(url, new MvcRouteHandler())
  17:     {
  18:         Defaults = CreateRouteValueDictionaryUncached(defaults),
  19:         Constraints = CreateRouteValueDictionaryUncached(constraints),
  20:         DataTokens = new RouteValueDictionary()
  21:     };
  22:  
  23:     ConstraintValidation.Validate(route);
  24:  
  25:     if ((namespaces != null) && (namespaces.Length > 0))
  26:     {
  27:         route.DataTokens[RouteDataTokenKeys.Namespaces] = namespaces;
  28:     }
  29:  
  30:     routes.Add(name, route);
  31:  
  32:     return route;
  33: }

 

三、请求到达真正的处理程序:MVCHandler

IRouteHandler 里只有一个方法 IHttpHandler GetHttpHandler();

   1: namespace System.Web.Routing
   2: {
   3:     // 摘要: 
   4:     //     定义类必须实现才能处理匹配路由模式的请求的协定。
   5:     [TypeForwardedFrom("System.Web.Routing, Version=3.5.0.0, Culture=Neutral, PublicKeyToken=31bf3856ad364e35")]
   6:     public interface IRouteHandler
   7:     {
   8:         // 摘要: 
   9:         //     提供处理请求的对象。//
  10:         // 参数: 
  11:         //   requestContext:
  12:         //     一个对象,封装有关请求的信息。
  13:         // 返回结果: 
  14:         //     一个处理请求的对象。
  15:         IHttpHandler GetHttpHandler(RequestContext requestContext);
  16:     }
  17: }

MvcRouteHandler 是 IRouteHandler的实现,它实现的GetHttpHandler如下:

   1: //IRouteHandler.IRouteHandler() 的实现如下
   2:         protected virtual IHttpHandler GetHttpHandler(RequestContext requestContext)
   3:         {
   4:             requestContext.HttpContext.SetSessionStateBehavior(GetSessionStateBehavior(requestContext));
   5:             //返回一个 MvcHandler的实例,至此,当IIS请求处理管道,执行熬 Handler.Exe 时,请求真正达到MVC
   6:             return new MvcHandler(requestContext);
   7:         }

 

 

 

终于找到了!

综上所述,一个请求从 IIS 到达 MvcRouteHandler 的顺序如下:

1、IIS接到请求:

1.1、IIS接到一个请求,检查请求的应用是否已初始化;
1.2、若应用未初始化,为应用分配应用池程序资源,及其他应用程序域信息,加载全局和本站web.config信息以设定配置;
1.3、开始应用初始化;

2、开始应用初始化:

2.1、在应用程序域,为应用程序创建环境对象(HostingEnvironment??)和响应对象(HttpContext、HttpRequest 和 HttpResponse);
2.2、创建应用的 HttpApplication 类型实例(即Global.asax.cs 实例),以启动应用;
2.3、在 Global.asax.cs 中,调用程序 RegisterRoutes 注册路由;
2.4、在 RegisterRoutes 中,调用 System.Web.Mvc.RouteCollectionExtensions.MapRoute() 逐条注册;
2.5、在 MapRoute中,直接把 MvcRouteHandler 类型实例塞到 System.Web.Routing 的初始化方法里,以填充 System.Web.Routing.RouteTable.Routes 数据;

3、初始化完成,处理请求:

3.1、HttpApplication 启动HTTP管道模型开始处理请求;
3.2、HTTP 管道处理已注册的 IHttpModule 事件:System.Web.Routing.UrlRoutingModule.OnApplicationPostResolveRequestCache();
3.3、随即 OnApplicationPostResolveRequestCache 调用 PostResolveRequestCache();
3.4、PostResolveRequestCache 方法从 System.Web.Routing.RouteTable.Routes 的数据中获取 IHttpHandler 类型;
3.5、在2.4中被直接塞入的 MvcRouteHandler 类型实例,被映射到 IIS HTTP处理管道中;
3.6、最终,IIS HTTP处理管道调用 MvcHandler 处理请求,并返回 Response 内容;

至此,请求 成功透过 Asp.Net 到达 MvcHandler 处理程序。

 

 

系列一共计划三篇

Asp.Net Routing与MVC 之一: 请求如何到达MVC

Asp.Net Routing与MVC 之二: 请求如何激活Controller和Action

Asp.Net Routing与MVC 之三: 路由在MVC的使用

 

 

 

 

 

 

参考了一堆文章,下边是传送门

----------------------------------------

 http://msdn.microsoft.com/zh-cn/library/bb470252%28v=vs.100%29.aspx 

 http://www.iis.net/learn/get-started/introduction-to-iis/introduction-to-iis-architecture 

 

 http://blog.csdn.net/darren__chan/article/details/8215646

 http://www.cnblogs.com/isdavid/archive/2013/05/28/3103228.html

 http://www.cnblogs.com/fsjohnhuang/articles/2332074.html

 http://www.bdqn.cn/news/201309/11384.shtml

----------------------------------------

posted @ 2014-07-26 10:38  学而不思则罔  阅读(679)  评论(0编辑  收藏  举报