mvc5 源码解析2-1：mvchandler的执行

上一节说在urlroutingmodule中mvchandler 映射到httpcontext上，那mvchandler又是怎么执行的呢？

（1）、httpruntime

从isapiruntime pr方法到httpruntime

ProcessRequestNoDemand(wr)方法

// System.Web.HttpRuntime

internal static void ProcessRequestNoDemand(HttpWorkerRequest wr)

{
　　//获取请求队列

    RequestQueue requestQueue = HttpRuntime._theRuntime._requestQueue;

    wr.UpdateInitialCounters();

    if (requestQueue != null)

    {

        wr = requestQueue.GetRequestToExecute(wr);

    }

    if (wr != null)

    {

        HttpRuntime.CalculateWaitTimeAndUpdatePerfCounter(wr);

        wr.ResetStartTime();

        HttpRuntime.ProcessRequestNow(wr);

    }

}

ProcessRequestNow(wr)方法

// System.Web.HttpRuntime

internal static void ProcessRequestNow(HttpWorkerRequest wr)

{

    HttpRuntime._theRuntime.ProcessRequestInternal(wr);

}

ProcessRequestInternal(wr)方法

// System.Web.HttpRuntime

private void ProcessRequestInternal(HttpWorkerRequest wr)

{
　　//活动请求数量增加

    Interlocked.Increment(ref this._activeRequestCount);
　　//判断请求数异常

    if (this._disposingHttpRuntime)

    {

        try

        {

            wr.SendStatus(, "Server Too Busy");

            wr.SendKnownResponseHeader(, "text/html; charset=utf-8");

            byte[] bytes = Encoding.ASCII.GetBytes("<html><body>Server Too Busy</body></html>");

            wr.SendResponseFromMemory(bytes, bytes.Length);

            wr.FlushResponse(true);

            wr.EndOfRequest();

        }

        finally

        {

            Interlocked.Decrement(ref this._activeRequestCount);

        }

        return;

    }

    HttpContext httpContext;

    try

    {
　　　　　　//HttpWorkerRequest转HttpContext

        httpContext = new HttpContext(wr, false);

    }

    catch

    {

        try

        {

            wr.SendStatus(, "Bad Request");

            wr.SendKnownResponseHeader(, "text/html; charset=utf-8");

            byte[] bytes2 = Encoding.ASCII.GetBytes("<html><body>Bad Request</body></html>");

            wr.SendResponseFromMemory(bytes2, bytes2.Length);

            wr.FlushResponse(true);

            wr.EndOfRequest();

            return;

        }

        finally

        {

            Interlocked.Decrement(ref this._activeRequestCount);

        }

    }

    wr.SetEndOfSendNotification(this._asyncEndOfSendCallback, httpContext);

    HostingEnvironment.IncrementBusyCount();

    try

    {

        try

        {

            this.EnsureFirstRequestInit(httpContext);

        }

        catch

        {

            if (!httpContext.Request.IsDebuggingRequest)

            {

                throw;

            }

        }

        httpContext.Response.InitResponseWriter();
　　　　//获取application实例

        IHttpHandler applicationInstance = HttpApplicationFactory.GetApplicationInstance(httpContext);

        if (applicationInstance == null)

        {

            throw new HttpException(SR.GetString("Unable_create_app_object"));

        }

        if (EtwTrace.IsTraceEnabled(, ))

        {

            EtwTrace.Trace(EtwTraceType.ETW_TYPE_START_HANDLER, httpContext.WorkerRequest, applicationInstance.GetType().FullName, "Start");

        }
　　　　//判断application实例是否有继承IHttpAsyncHandler

        if (applicationInstance is IHttpAsyncHandler)

        {

            IHttpAsyncHandler httpAsyncHandler = (IHttpAsyncHandler)applicationInstance;

            httpContext.AsyncAppHandler = httpAsyncHandler;
　　　　　　　　//执行application的BeginProcessRequest

            httpAsyncHandler.BeginProcessRequest(httpContext, this._handlerCompletionCallback, httpContext);

        }

        else

        {

            applicationInstance.ProcessRequest(httpContext);

            this.FinishRequest(httpContext.WorkerRequest, httpContext, null);

        }

    }

    catch (Exception e)

    {

        httpContext.Response.InitResponseWriter();

        this.FinishRequest(wr, httpContext, e);

    }

}

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 httpAsyncResult = new HttpAsyncResult(cb, extraData);

            this.AsyncResult = httpAsyncResult;

            if (this._context.TraceIsEnabled)

            {

                HttpRuntime.Profile.StartRequest(this._context);

            }
　　　　　　　　//执行步骤

            this.ResumeSteps(null);

            return httpAsyncResult;

        }

ResumeSteps方法

private void ResumeSteps(Exception error)

        {

            this._stepManager.ResumeSteps(error);

        }

this._stepManager 抽象类

internal abstract class StepManager

        {

            protected HttpApplication _application;

            protected bool _requestCompleted;

            internal bool IsCompleted

            {

                get

                {

                    return this._requestCompleted;

                }

            }

            internal StepManager(HttpApplication application)

            {

                this._application = application;

            }

            internal abstract void BuildSteps(WaitCallback stepCallback);

            internal void CompleteRequest()

            {

                this._requestCompleted = true;

                if (HttpRuntime.UseIntegratedPipeline)

                {

                    HttpContext context = this._application.Context;

                    if (context != null && context.NotificationContext != null)

                    {

                        context.NotificationContext.RequestCompleted = true;

                    }

                }

            }

            internal abstract void InitRequest();

            internal abstract void ResumeSteps(Exception error);

        }

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mvc5 源码解析2-1：mvchandler的执行

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