internal class MapHandlerExecutionStep : HttpApplication.IExecutionStep
{
// Fields
private HttpApplication _application;
// Methods
internal MapHandlerExecutionStep(HttpApplication app)
{
this._application = app;
}
void HttpApplication.IExecutionStep.Execute()
{
HttpContext context = this._application.Context;
HttpRequest request = context.Request;
if (EtwTrace.IsTraceEnabled(5, 1))
{
EtwTrace.Trace(EtwTraceType.ETW_TYPE_MAPHANDLER_ENTER, context.WorkerRequest);
}
context.Handler = this._application.MapHttpHandler(context, request.RequestType, request.FilePathObject, request.PhysicalPathInternal, false);
if (EtwTrace.IsTraceEnabled(5, 1))
{
EtwTrace.Trace(EtwTraceType.ETW_TYPE_MAPHANDLER_LEAVE, context.WorkerRequest);
}
}
// Properties
bool HttpApplication.IExecutionStep.CompletedSynchronously
{
get
{
return true;
}
}
bool HttpApplication.IExecutionStep.IsCancellable
{
get
{
return false;
}
}
}
里面的调用主要是
context.Handler = this._application.MapHttpHandler(context, request.RequestType, request.FilePathObject, request.PhysicalPathInternal, false);
而HttpApplication的MapHttpHandler如下：
复制代码 代码如下:
internal IHttpHandler MapHttpHandler(HttpContext context, string requestType, VirtualPath path, string pathTranslated, bool useAppConfig)
{
IHttpHandler handler = (context.ServerExecuteDepth == 0) ? context.RemapHandlerInstance : null;
using (new ApplicationImpersonationContext())
{
if (handler != null)
{
return handler;
}
HttpHandlerAction mapping = this.GetHandlerMapping(context, requestType, path, useAppConfig);
if (mapping == null)
{
PerfCounters.IncrementCounter(AppPerfCounter.REQUESTS_NOT_FOUND);
PerfCounters.IncrementCounter(AppPerfCounter.REQUESTS_FAILED);
throw new HttpException(SR.GetString("Http_handler_not_found_for_request_type", new object[] { requestType }));
}
IHttpHandlerFactory factory = this.GetFactory(mapping);
try
{
IHttpHandlerFactory2 factory2 = factory as IHttpHandlerFactory2;
if (factory2 != null)
{
handler = factory2.GetHandler(context, requestType, path, pathTranslated);
}
else
{
handler = factory.GetHandler(context, requestType, path.VirtualPathString, pathTranslated);
}
}
catch (FileNotFoundException exception)
{
if (HttpRuntime.HasPathDiscoveryPermission(pathTranslated))
{
throw new HttpException(0x194, null, exception);
}
throw new HttpException(0x194, null);
}
catch (DirectoryNotFoundException exception2)
{
if (HttpRuntime.HasPathDiscoveryPermission(pathTranslated))
{
throw new HttpException(0x194, null, exception2);
}
throw new HttpException(0x194, null);
}
catch (PathTooLongException exception3)
{
if (HttpRuntime.HasPathDiscoveryPermission(pathTranslated))
{
throw new HttpException(0x19e, null, exception3);
}
throw new HttpException(0x19e, null);
}
if (this._handlerRecycleList == null)
{
this._handlerRecycleList = new ArrayList();
}
this._handlerRecycleList.Add(new HandlerWithFactory(handler, factory));
}
return handler;
}
在MapHttpHandler里创建了IHttpHandlerFactory，进而创建了httphandler。
在ApplicationStepManager中BuildSteps的方法有steps.Add(new HttpApplication.CallHandlerExecutionStep(app));这么一句，这就是注册调用我们hanndler的地方。
复制代码 代码如下: