通过.NET Reflerctor我们可以反编译看一个请求是如何被响应处理的。以下为请求被响应处理的过程涉及到的主要类
- ISAPIRuntime
- HttpRuntime
- HttpApplicationFactory
- HttpApplication
- HttpContext
- HttpModule
- HttpHanler
使用.net reflerctor读取.net 3.5 frameword类库
一、请求如何到达w3wp.exe进程
当站点已部署在IIS下时,这时有客户端请求到达,首先被www服务进程inetinfo.exe捕获,根据请求页面的后缀名由IIS配置处理程序映射的dll处理,如果是aspx页面就交由aspnet_isapi.dll处理,aspnet_isapi.dll再将请求分发给w3wp.exe进程(也就是我们在VS调试的时候附加的进程)。
二、如何创建HttpApplication管线
w3wp.exe进程先调用System.Web.Hosting下的ISAPIRuntime.ProcessRequest方法触发HttpRuntime
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public int ProcessRequest(IntPtr ecb, int iWRType) { IntPtr zero = IntPtr.Zero; if (iWRType == 2 ) { zero = ecb; ecb = UnsafeNativeMethods.GetEcb(zero); } ISAPIWorkerRequest wr = null ; try { bool useOOP = iWRType == 1 ; wr = ISAPIWorkerRequest.CreateWorkerRequest(ecb, useOOP); wr.Initialize(); string appPathTranslated = wr.GetAppPathTranslated(); string appDomainAppPathInternal = HttpRuntime.AppDomainAppPathInternal; if ((appDomainAppPathInternal == null ) || StringUtil.EqualsIgnoreCase(appPathTranslated, appDomainAppPathInternal)) { HttpRuntime.ProcessRequestNoDemand(wr); return 0 ; } HttpRuntime.ShutdownAppDomain(ApplicationShutdownReason.PhysicalApplicationPathChanged, SR.GetString( " Hosting_Phys_Path_Changed " , new object [] { appDomainAppPathInternal, appPathTranslated })); return 1 ; } catch (Exception exception) { try { WebBaseEvent.RaiseRuntimeError(exception, this ); } catch { } if ((wr == null ) || ! (wr.Ecb == IntPtr.Zero)) { throw ; } if (zero != IntPtr.Zero) { UnsafeNativeMethods.SetDoneWithSessionCalled(zero); } if (exception is ThreadAbortException) { Thread.ResetAbort(); } return 0 ; } }
ISAPIRuntime生成了一个HttpWorkerRequest对象(即HttpContext.Current),并传递给HttpRuntime。接着执行HttpRuntime.ProcessRequestNoDemand方法
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internal static void ProcessRequestNoDemand(HttpWorkerRequest wr) { RequestQueue queue = _theRuntime._requestQueue; if (queue != null ) { wr = queue.GetRequestToExecute(wr); } if (wr != null ) { CalculateWaitTimeAndUpdatePerfCounter(wr); wr.ResetStartTime(); ProcessRequestNow(wr); } }
转到HttpRuntime.ProcessRequestNow方法
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internal static void ProcessRequestNow(HttpWorkerRequest wr) { _theRuntime.ProcessRequestInternal(wr); }
继续调用HttpRuntime.ProcessRequestInternal方法
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private void ProcessRequestInternal(HttpWorkerRequest wr) { HttpContext context; try { context = new HttpContext(wr, false ); } catch { wr.SendStatus( 400 , " Bad Request " ); wr.SendKnownResponseHeader( 12 , " text/html; charset=utf-8 " ); byte [] bytes = Encoding.ASCII.GetBytes( " <html><body>Bad Request</body></html> " ); wr.SendResponseFromMemory(bytes, bytes.Length); wr.FlushResponse( true ); wr.EndOfRequest(); return ; } wr.SetEndOfSendNotification( this ._asyncEndOfSendCallback, context); Interlocked.Increment( ref this ._activeRequestCount); HostingEnvironment.IncrementBusyCount(); try { try { this .EnsureFirstRequestInit(context); } catch { if ( ! context.Request.IsDebuggingRequest) { throw ; } } context.Response.InitResponseWriter(); IHttpHandler applicationInstance = HttpApplicationFactory.GetApplicationInstance(context); if (applicationInstance == null ) { throw new HttpException(SR.GetString( " Unable_create_app_object " )); } if (EtwTrace.IsTraceEnabled( 5 , 1 )) { EtwTrace.Trace(EtwTraceType.ETW_TYPE_START_HANDLER, context.WorkerRequest, applicationInstance.GetType().FullName, " Start " ); } if (applicationInstance is IHttpAsyncHandler) { IHttpAsyncHandler handler2 = (IHttpAsyncHandler) applicationInstance; context.AsyncAppHandler = handler2; handler2.BeginProcessRequest(context, this ._handlerCompletionCallback, context); } else { applicationInstance.ProcessRequest(context); this .FinishRequest(context.WorkerRequest, context, null ); } } catch (Exception exception) { context.Response.InitResponseWriter(); this .FinishRequest(wr, context, exception); } }
该方法创建了我们在后面经常用到的HttpContext上下文(请求与响应信息),接着通过 HttpApplicationFactory获取HttpApplication实例。
仔细看一下IHttpHandler
applicationInstance = HttpApplicationFactory.GetApplicationInstance(context) 方法
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internal static IHttpHandler GetApplicationInstance(HttpContext context) { if (_customApplication != null ) { return _customApplication; } if (context.Request.IsDebuggingRequest) { return new HttpDebugHandler(); } _theApplicationFactory.EnsureInited(); _theApplicationFactory.EnsureAppStartCalled(context); return _theApplicationFactory.GetNormalApplicationInstance(context); }
如果HttpApplication实例存在就直接返回,不存就先执行_theApplicationFactory.EnsureInited();
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private void EnsureInited() { if ( ! this ._inited) { lock ( this ) { if ( ! this ._inited) { this .Init(); this ._inited = true ; } } } }
调用HttpApplicationFactory的Init方法(HttpApplicationFactory是单例模式)
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private void Init() { if (_customApplication == null ) { try { try { this ._appFilename = GetApplicationFile(); this .CompileApplication(); } finally { this .SetupChangesMonitor(); } } catch { throw ; } } }
主要看两个方法
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internal static string GetApplicationFile() { return Path.Combine(HttpRuntime.AppDomainAppPathInternal, " global.asax " ); } private void SetupChangesMonitor() { FileChangeEventHandler callback = new FileChangeEventHandler( this .OnAppFileChange); HttpRuntime.FileChangesMonitor.StartMonitoringFile( this ._appFilename, callback); if ( this ._fileDependencies != null ) { foreach ( string str in this ._fileDependencies) { HttpRuntime.FileChangesMonitor.StartMonitoringFile(HostingEnvironment.MapPathInternal(str), callback); } } }
读取global.asax文件(很熟悉吧,应用程序的全局配置文件),并添加事件监视。
再回到GetApplicationInstance方法中,执行_theApplicationFactory.GetNormalApplicationInstance(context) 从_freeList读取HttpApplication实例
或者通过反射创建新的HttpApplication实例。
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private HttpApplication GetNormalApplicationInstance(HttpContext context) { HttpApplication application = null ; lock ( this ._freeList) { if ( this ._numFreeAppInstances > 0 ) { application = (HttpApplication) this ._freeList.Pop(); this ._numFreeAppInstances -- ; if ( this ._numFreeAppInstances < this ._minFreeAppInstances) { this ._minFreeAppInstances = this ._numFreeAppInstances; } } } if (application == null ) { application = (HttpApplication) HttpRuntime.CreateNonPublicInstance( this ._theApplicationType); using ( new ApplicationImpersonationContext()) { application.InitInternal(context, this ._state, this ._eventHandlerMethods); } } return application; }
三、何时加载HttpModule
当HttpApplication首次被创建的时候,我们可以看到上面的方法的实例化调用了HttpApplication的方法
application.InitInternal(context,
this._state,
this._eventHandlerMethods),这个方法将首先将HttpApplication实例绑到
HttpContext.ApplicationInstance 上,这样我们通过上下文可以找到HttpApplication实例。接着又调用了
this.InitModules()
去加载配置文件中的HttpModule
private void InitModules() { this ._moduleCollection = RuntimeConfig.GetAppConfig().HttpModules.CreateModules(); this .InitModulesCommon(); } private void InitModulesCommon() { int count = this ._moduleCollection.Count; for ( int i = 0 ; i < count; i ++ ) { this ._currentModuleCollectionKey = this ._moduleCollection.GetKey(i); this ._moduleCollection[i].Init( this ); } this ._currentModuleCollectionKey = null ; this .InitAppLevelCulture(); }
Module被反射加载后,在InitMoulesCommon中会调会HttpModule的Init方法。
我们来看一配置文件,Module加载是按照配置文件的顺序,所以事件被触发也是按照这个顺序。另外.net 的module是优先加载的,例如Session等。
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< httpModules > < add name = " ScriptModule " type = " System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35 " /> < add name = " UrlRoutingModule " type = " System.Web.Routing.UrlRoutingModule, System.Web.Routing, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35 " /> </ httpModules >
我们再回HttpApplication的 InitInternal方法,当 InitModules()创建HttpModuleCollection后,在HookupEventHandlersForApplicationAndModules方法中绑定Module的事件处理
接着就是HttpApplication的管线事件和HttpHandler的有序绑定。
接着就是HttpApplication的管线事件和HttpHandler的有序绑定。
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if (HttpRuntime.UseIntegratedPipeline) { this ._stepManager = new PipelineStepManager( this ); } else { this ._stepManager = new ApplicationStepManager( this ); } this ._stepManager.BuildSteps( this ._resumeStepsWaitCallback);
ApplicationManager和PipelineStepManager都继随自HttpApplication.StepManager。SetpManager主HttpApplication的内部调度类,主要负责HttpApplication管线的事件和HttpHandler有序绑定和执行工作。
题外话:HttpApplication本身不对请求做任何处理,而是交由HttpModule与HttpHandler,而HttpModule不仅决定了使用什么HttpHandler,并且还可以修改请求和响应信息。当HttpModule把处理权交给HttpHandler后,HttpHandler才能从上下文取出请求做相应处理。(WebForm与MVC差别从这里开始不同了)。
四、HttpHandler
HttpHandler是我们真正.net 程序处理代码的位置(Page,Controller,Session操作等等)
BuildSteps方法在绑定事件的同时,其中红色标记位加载了映射和要执行的HttpHandler
里只是建立了好管线事件的触发顺序以及HttpHandler的加载与执行句柄等,但是直正触发管道执行的,还是要回到HttpRuntime的
ProcessRequestInternal的方法中。
steps.
Add(
new HttpApplication.MapHandlerExecutionStep(app))添加加载反射HttpHandler的MapHandlerExecutionSte到Steps中;注意他的Execute方法是加载。
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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 ; } } }
steps.Add(
new HttpApplication.CallHandlerExecutionStep(app));这个CallHandlerExecutionStep是触发HttpHandler的Step,我们来看一下他的Exectue方法
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internal class CallHandlerExecutionStep : HttpApplication.IExecutionStep { // Fields private HttpApplication _application; private AsyncCallback _completionCallback; private IHttpAsyncHandler _handler; private bool _sync; // Methods internal CallHandlerExecutionStep(HttpApplication app) { this ._application = app; this ._completionCallback = new AsyncCallback( this .OnAsyncHandlerCompletion); } private void OnAsyncHandlerCompletion(IAsyncResult ar) { if ( ! ar.CompletedSynchronously) { HttpContext context = this ._application.Context; Exception error = null ; try { try { this ._handler.EndProcessRequest(ar); } finally { context.Response.GenerateResponseHeadersForHandler(); } } catch (Exception exception2) { if ((exception2 is ThreadAbortException) || ((exception2.InnerException != null ) && (exception2.InnerException is ThreadAbortException))) { this ._application.CompleteRequest(); } else { error = exception2; } } if (EtwTrace.IsTraceEnabled( 4 , 4 )) { EtwTrace.Trace(EtwTraceType.ETW_TYPE_HTTPHANDLER_LEAVE, context.WorkerRequest); } this ._handler = null ; context.SetStartTime(); this .ResumeStepsWithAssert(error); } } [PermissionSet(SecurityAction.Assert, Unrestricted = true )] private void ResumeStepsWithAssert(Exception error) { this ._application.ResumeStepsFromThreadPoolThread(error); } void HttpApplication.IExecutionStep.Execute() { HttpContext context = this ._application.Context; IHttpHandler handler = context.Handler; if (EtwTrace.IsTraceEnabled( 4 , 4 )) { EtwTrace.Trace(EtwTraceType.ETW_TYPE_HTTPHANDLER_ENTER, context.WorkerRequest); } if ((handler != null ) && HttpRuntime.UseIntegratedPipeline) { IIS7WorkerRequest workerRequest = context.WorkerRequest as IIS7WorkerRequest; if ((workerRequest != null ) && workerRequest.IsHandlerExecutionDenied()) { this ._sync = true ; HttpException exception = new HttpException( 0x193 , SR.GetString( " Handler_access_denied " )); exception.SetFormatter( new PageForbiddenErrorFormatter(context.Request.Path, SR.GetString( " Handler_access_denied " ))); throw exception; } } if (handler == null ) { this ._sync = true ; } else if (handler is IHttpAsyncHandler) { IHttpAsyncHandler handler2 = (IHttpAsyncHandler) handler; this ._sync = false ; this ._handler = handler2; IAsyncResult result = handler2.BeginProcessRequest(context, this ._completionCallback, null ); if (result.CompletedSynchronously) { this ._sync = true ; this ._handler = null ; try { handler2.EndProcessRequest(result); } finally { context.Response.GenerateResponseHeadersForHandler(); } if (EtwTrace.IsTraceEnabled( 4 , 4 )) { EtwTrace.Trace(EtwTraceType.ETW_TYPE_HTTPHANDLER_LEAVE, context.WorkerRequest); } } } else { this ._sync = true ; context.SyncContext.SetSyncCaller(); try { handler.ProcessRequest(context); } finally { context.SyncContext.ResetSyncCaller(); if (EtwTrace.IsTraceEnabled( 4 , 4 )) { EtwTrace.Trace(EtwTraceType.ETW_TYPE_HTTPHANDLER_LEAVE, context.WorkerRequest); } context.Response.GenerateResponseHeadersForHandler(); } } } // Properties bool HttpApplication.IExecutionStep.CompletedSynchronously { get { return this ._sync; } } bool HttpApplication.IExecutionStep.IsCancellable { get { return ! ( this ._application.Context.Handler is IHttpAsyncHandler); } } }
注意Execute方法调用了HttpHandler的BeginProcessRequest或ProcessRequst。这就HttpHandler的直正接手处理请求的入口,但这里都StepManager的准备工作。
它的触发过程:->HttpRuntime获取到HttpApplication,并调用的HttpApplication.BeginProcessRequest->HttpApplication.StepManager.ResumeSteps
->HttpApplication.StepManager._execSteps[i].Execute ->HttpHandler.ProcessRequest
当通过IHttpHandler
applicationInstance = HttpApplicationFactory.GetApplicationInstance(context); 获取实例后,HttpRuntime开始触发application的请求处理
即调用HttpApplication的BeginProcessRequest方法
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if (applicationInstance is IHttpAsyncHandler) { IHttpAsyncHandler handler2 = (IHttpAsyncHandler) applicationInstance; context.AsyncAppHandler = handler2; handler2.BeginProcessRequest(context, this ._handlerCompletionCallback, context); } else { applicationInstance.ProcessRequest(context); this .FinishRequest(context.WorkerRequest, context, null ); }
看一下BeginProcessRequest方法
IAsyncResult IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData) { this ._context = context; this ._context.ApplicationInstance = this ; this ._stepManager.InitRequest(); this ._context.Root(); HttpAsyncResult result = new HttpAsyncResult(cb, extraData); this .AsyncResult = result; if ( this ._context.TraceIsEnabled) { HttpRuntime.Profile.StartRequest( this ._context); } this .ResumeSteps( null ); return result; } void IHttpHandler.ProcessRequest(HttpContext context) { throw new HttpException(SR.GetString( " Sync_not_supported " )); }
BeginProcessRequest方法调用
StepManager的InitRequest(初始化执行顺序的参数),然后接着调用了最重要的
ResumeSteps方法,此方法将按顺序执行
StepManager中保存HttpApplication绑定的事件及HttpHandler。
分析一下
ResumeSteps 方法
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[DebuggerStepperBoundary] internal override void ResumeSteps(Exception error) { bool flag = false ; bool completedSynchronously = true ; HttpApplication application = base ._application; HttpContext context = application.Context; HttpApplication.ThreadContext context2 = null ; AspNetSynchronizationContext syncContext = context.SyncContext; lock ( base ._application) { try { context2 = application.OnThreadEnter(); } catch (Exception exception) { if (error == null ) { error = exception; } } try { try { Label_0040: if (syncContext.Error != null ) { error = syncContext.Error; syncContext.ClearError(); } if (error != null ) { application.RecordError(error); error = null ; } if (syncContext.PendingOperationsCount > 0 ) { syncContext.SetLastCompletionWorkItem( this ._resumeStepsWaitCallback); } else { if (( this ._currentStepIndex < this ._endRequestStepIndex) && ((context.Error != null ) || base ._requestCompleted)) { context.Response.FilterOutput(); this ._currentStepIndex = this ._endRequestStepIndex; } else { this ._currentStepIndex ++ ; } if ( this ._currentStepIndex >= this ._execSteps.Length) { flag = true ; } else { this ._numStepCalls ++ ; context.SyncContext.Enable(); error = application.ExecuteStep( this ._execSteps[ this ._currentStepIndex], ref completedSynchronously); if (completedSynchronously) { this ._numSyncStepCalls ++ ; goto Label_0040; } } } } finally { if (context2 != null ) { try { context2.Leave(); } catch { } } } } catch { throw ; } } if (flag) { context.Unroot(); application.AsyncResult.Complete( this ._numStepCalls == this ._numSyncStepCalls, null , null ); application.ReleaseAppInstance(); } }
留意代码会发现
Label_0040
this._currentStepIndex++;
error = application.ExecuteStep(
this._execSteps[
this._currentStepIndex],
ref completedSynchronously);
goto Label_0040;
每执行完
StepManager中_execSteps保存事件或httpHandler就+1 goto 到下一次的事件或httpHandler。
ExecuteStep调用了 step.Execute(),接着Execute又执行了HttpHandler的ProecessRequest方法。这个时候请求就直正交到了HttpHandler手里处理了。
以下HttpApplication管线执行先后顺序,订阅事件,HttpModule,HttpHanlder加载与执行位置(参照博文:
ASP.NET MVC Preview生命周期分析)
HttpApplication 管线会依次处理下面的请求:
-
对请求进行验证,将检查浏览器发送的信息,并确定其是否包含潜在恶意标记。
-
如果已在 Web.config 文件的 UrlMappingsSection 节中配置了任何 URL,则执行 URL 映射。
-
引发 BeginRequest 事件。
-
引发 AuthenticateRequest 事件。
-
引发 PostAuthenticateRequest 事件。
-
引发 AuthorizeRequest 事件。
-
引发 PostAuthorizeRequest 事件。
-
引发 ResolveRequestCache 事件。
-
引发 PostResolveRequestCache 事件。通知HttpModule根据请求选择对应的HttpHnadler加载至上下文中。
-
根据所请求资源的文件扩展名(在应用程序的配置文件中映射),选择实现 IHttpHandler 的类,对请求进行处理。如果该请求针对从 Page 类派生的对象(页),并且需要对该页进行编译,则 ASP.NET 会在创建该页的实例之前对其进行编译。(除了配置文件中的,还有上下文中的HttpHnadler)
-
引发 PostMapRequestHandler 事件。继续通知HttpModule确定要使用哪个HttpHandler用以处理请求。
-
引发 AcquireRequestState 事件。
-
引发 PostAcquireRequestState 事件。
-
引发 PreRequestHandlerExecute 事件。
-
为该请求调用合适的 IHttpHandler 类的 ProcessRequest 方法(或异步版 BeginProcessRequest)。例如,如果该请求针对某页,则当前的页实例将处理该请求。
-
引发 PostRequestHandlerExecute 事件。
-
引发 ReleaseRequestState 事件。
-
引发 PostReleaseRequestState 事件。
-
如果定义了 Filter 属性,则执行响应筛选。
-
引发 UpdateRequestCache 事件。
-
引发 PostUpdateRequestCache 事件。
-
引发 EndRequest 事件。
小结:
理一下前后的过程
ISAPIRuntime 调用至HttpRuntime , HttpRuntime 通过HttpApplicationFactory 获取HttpApplication,HttpApplication在生成的同时加载了所有的HttpMoudule,并且通过StepManager完
成对管线事件绑定及HttpHandler的加载。然后HttpRuntime 触发HttpApplication 的BeginProcessRequest开始了真正的HttpRequest请求的处理过程。
HttpApplication按照管线StepManager事先设定好的事件触发顺序,当被HttpModule订阅的事件发生,HttpModule根据请求的信息加载对应的HttpHandler到上下文中,并把控制权还给管线。
HttpApplication继续按照管线进行,将所有的HttpHandler加载进来。之后过程中通过HttpModule确定使用哪个HttpHandler处理请求,直到管线调用这个 HttpHandler的ProcessRequest,这个时候HttpHandler才开始着手处理上下文中的请求,比如查找请求的具体页面地址,调用请求的方法,绘制视图等等。
HttpHandler 处理完后,HttpApplication管线又将上下文的控制交还给HttpModule,HttpModule对请求最后处理后,又把控制权还给管线继续处理下面的事件,直到HttpRuntime 结束请求返回客户端。
以上是为.net MVC 实现机制分析做的铺垫。