How asp.net MVC works (3): Controller activation

asp.net MVC url Routing system resolves HTTP requests through registered routing tables to obtain a Routedata object for encapsulating routing data. This process is accomplished by registering the HttpApplication Postresolverequestcache event with a custom urlroutingmodule. Routedata already contains the name of the target controller, let's further analyze how the real controller object is activated. We first need to understand a type with a type of mvcroutehandler.

First, Mvcroutehandler

We know from the previous introduction that the route type inherited from RouteBase has a property of type Iroutehandler interface Routehandler, Its main purpose is to obtain a HttpHandler object based on the specified request context (represented by a RequestContext object). When the Getroutedata method is executed, the value of the route's Routehandler property is reflected on the resulting Routedata property of the same name. By default, the route Routehandler property is a Mvcroutehandler object, as the following code fragment reflects this.

   1:public class Route:routebase
   2: {
   3:     //other Members
   4: Public     iroutehandler Routehandler {get; set;}
   5: Public     Route ()
   6:     {
   7:         //Other operations
   8: This         . Routehandler = new Mvcroutehandler ();
   9:     }
  10:}

For our mini version of the ASP.net MVC framework, Mvcroutehandler is a type with the following definitions. In the Gethttphandler method of implementation, it returns a Mvchandler object directly.

   1:public class Mvcroutehandler:iroutehandler
   2: {
   3: Public     IHttpHandler Gethttphandler (RequestContext requestcontext)
   4:     {
   5: Return         new Mvchandler (RequestContext);
   6:     }
   7:}

Second, Mvchandler

As we have mentioned in the previous section, the entire ASP.NET MVC framework is implemented through a custom HttpModule and HttpHandler object asp.net extension. This custom HttpModule we have already introduced, is UrlRoutingModule, and this custom HttpHandler is we want to focus on Mvchandler.

UrlRoutingModule after parsing the HTTP request through the routing table to get a routedata to encapsulate the routing data, or call its Routehandler Gethttphandler method to get the HttpHandler object and register it with the current HTTP context. Because the routehandler of routedata originates from the routehandler of the corresponding route object, which is a Mvcroutehandler object by default, So this is the Mvchandler object that is used to handle HTTP requests by default. Mvchandler implements the activation of the Controller object and the execution of the corresponding action method.

The following code fragment embodies the entire definition of Mvchandler, which has a property of type RequestContext representing the current request context being processed, which is specified in the constructor. The activation and execution of the Controller object is realized in the implementation of the ProcessRequest.

   1:public class Mvchandler:ihttphandler
   2: {
   3: Public     bool IsReusable
   4:     {
   5:         Get{return false;
   6:     }
   7: Public     requestcontext RequestContext {get; private set;}
   8: Public     Mvchandler (RequestContext requestcontext)
   9:     {
  A: this         . RequestContext = RequestContext;
  One:     }
  : Public     void ProcessRequest (HttpContext context)
  :     {
           string controllername = this. RequestContext.RouteData.Controller;
  :         icontrollerfactory controllerfactory = ControllerBuilder.Current.GetControllerFactory ();
  :         IController controller = Controllerfactory.createcontroller (this. RequestContext, controllername);
  :         Controller. Execute (this. RequestContext);
  :     }
  19:}