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Asp.Net底层原理(三、Asp.Net请求响应过程)

时间:2013-09-17 09:36来源:未知 作者:admin 点击:我要投稿  高质量的ASP.NET空间,完美支持1.0/2.0/3.5/4.0/MVC等

浏览器封装请求报文,发送请求到达服务器,服务器内核模块的HTTP.SYS监听到用户的HTTP请求,将其分发给W3SVC,W3SVC解析出请求的URL,并根据Metabase获取映射关系得到目标应用,如果是静态资源(HTML,jss,img等),则将内容以HTTP响应的车型是返回。如果是动态文件(aspx、ashx)等,则进一步获取到目标对应的工作进程w3wp.exe,如果不存在,则创建一个新的工作进程。工作进程w3wp.exe利用aspnet_isapi.dll创建处理当前请求的应用程序域,随后ISAPIRuntime会被加载,ISAPIRuntime会接管该HTTP请求。

ISAPIRuntime会首先创建一个ISAPIWorkRequest对象,对请求报文进行了简单的封装,并将该ISAPIWorkRequest对象传递给HttpRuntime。

HttpRuntime会根据ISAPIWorkRequest创建用于封装Http请求上下文的对象HttpConetxt。

  HttpContext主要包括HttpRequest(当前请求)和HttpResponse(服务器响应)

 1 [SecurityPermission(SecurityAction.LinkDemand, Unrestricted=true)]
 2 public int ProcessRequest(IntPtr ecb, int iWRType)
 3 {
 4     IntPtr zero = IntPtr.Zero;
 5     if (iWRType == 2)
 6     {
 7         zero = ecb;
 8         ecb = UnsafeNativeMethods.GetEcb(zero);
 9     }
10     //创建了ISAPIWorkRquest空对象
11     ISAPIWorkerRequest wr = null;
12     try
13     {
14         bool useOOP = iWRType == 1;
15     //通过ecb句柄创建了ISAPIWorkRequest对象
16         wr = ISAPIWorkerRequest.CreateWorkerRequest(ecb, useOOP);
17         wr.Initialize();
18         string appPathTranslated = wr.GetAppPathTranslated();
19         string appDomainAppPathInternal = HttpRuntime.AppDomainAppPathInternal;
20         if ((appDomainAppPathInternal == null) || StringUtil.EqualsIgnoreCase(appPathTranslated, appDomainAppPathInternal))
21         {
22         //IsapiRuntime把WR交给了HttpRuntime
23             HttpRuntime.ProcessRequestNoDemand(wr);
24             return 0;
25         }
26         HttpRuntime.ShutdownAppDomain(ApplicationShutdownReason.PhysicalApplicationPathChanged, SR.GetString("Hosting_Phys_Path_Changed", new object[] { appDomainAppPathInternal, appPathTranslated }));
27         return 1;
28     }
29     catch (Exception exception)
30     {
31         try
32         {
33             WebBaseEvent.RaiseRuntimeError(exception, this);
34         }
35         catch
36         {
37         }
38         if ((wr == null) || !(wr.Ecb == IntPtr.Zero))
39         {
40             throw;
41         }
42         if (zero != IntPtr.Zero)
43         {
44             UnsafeNativeMethods.SetDoneWithSessionCalled(zero);
45         }
46         if (exception is ThreadAbortException)
47         {
48             Thread.ResetAbort();
49         }
50         return 0;
51     }
52 }
53 
54  
ISAPIRuntime

HttpRuntime通过HttpApplicationFactory获取一个新的或现有的HttpApplication对象。

 1 private void ProcessRequestInternal(HttpWorkerRequest wr)
 2 {
 3     Interlocked.Increment(ref this._activeRequestCount);
 4     if (this._disposingHttpRuntime)
 5     {
 6         try
 7         {
 8             wr.SendStatus(0x1f7, "Server Too Busy");
 9             wr.SendKnownResponseHeader(12, "text/html; charset=utf-8");
10             byte[] bytes = Encoding.ASCII.GetBytes("<html><body>Server Too Busy</body></html>");
11             wr.SendResponseFromMemory(bytes, bytes.Length);
12             wr.FlushResponse(true);
13             wr.EndOfRequest();
14         }
15         finally
16         {
17             Interlocked.Decrement(ref this._activeRequestCount);
18         }
19     }
20     else
21     {
22         HttpContext context;
23         try
24         {
25         //通过wr创建了上下文对象
26             context = new HttpContext(wr, false);
27         }
28         catch
29         {
30             try
31             {
32                 wr.SendStatus(400, "Bad Request");
33                 wr.SendKnownResponseHeader(12, "text/html; charset=utf-8");
34                 byte[] data = Encoding.ASCII.GetBytes("<html><body>Bad Request</body></html>");
35                 wr.SendResponseFromMemory(data, data.Length);
36                 wr.FlushResponse(true);
37                 wr.EndOfRequest();
38                 return;
39             }
40             finally
41             {
42                 Interlocked.Decrement(ref this._activeRequestCount);
43             }
44         }
45         wr.SetEndOfSendNotification(this._asyncEndOfSendCallback, context);
46         HostingEnvironment.IncrementBusyCount();
47         try
48         {
49             try
50             {
51                 this.EnsureFirstRequestInit(context);
52             }
53             catch
54             {
55                 if (!context.Request.IsDebuggingRequest)
56                 {
57                     throw;
58                 }
59             }
60             context.Response.InitResponseWriter();
61         
62         //通过HttpApplicationFactory获取HttpApplication实例
63             IHttpHandler applicationInstance = HttpApplicationFactory.GetApplicationInstance(context);
64             if (applicationInstance == null)
65             {
66                 throw new HttpException(SR.GetString("Unable_create_app_object"));
67             }
68             if (EtwTrace.IsTraceEnabled(5, 1))
69             {
70                 EtwTrace.Trace(EtwTraceType.ETW_TYPE_START_HANDLER, context.WorkerRequest, applicationInstance.GetType().FullName, "Start");
71             }
72             if (applicationInstance is IHttpAsyncHandler)
73             {
74                 IHttpAsyncHandler handler2 = (IHttpAsyncHandler) applicationInstance;
75                 context.AsyncAppHandler = handler2;
76 
77             //执行HttpApplication的BeginProcessRequest方法
78                 handler2.BeginProcessRequest(context, this._handlerCompletionCallback, context);
79             }
80             else
81             {
82                 applicationInstance.ProcessRequest(context);
83                 this.FinishRequest(context.WorkerRequest, context, null);
84             }
85         }
86         catch (Exception exception)
87         {
88             context.Response.InitResponseWriter();
89             this.FinishRequest(wr, context, exception);
90         }
91     }
92 }
HttpRuntime

HttpApplication负责处理分发给它的请求。由于一个HttpApplication对象在同一时间只能处理一个请求,只有完成对某个请求的处理后,HttpApplication才能用于后续请求  的处理,所以Asp.Net采用对象池的获取HttpApplication对象。

  

当第一个请求到达时,HttpApplicationFactory会一次创建多个HttpApplication对象,并将其置于对象池中,选择其中一个对象来处理该请求。处理完毕后HttpApplication不会回收,而是释放到池中。池中空闲的HttpApplication对象用于处理后续请求,当没有空闲的时候再进行创建新的HttpApplication。    

  HttpApplication对象的创建时根据Global文件编译后的类型,通过反射的方式创建的,很消耗资源和时间,因此这里使用了对象池的技术

    1.确保Global文件被编译,如果没有Global文件,则对所有事件提供HttpApplication的默认行为。

      Global:它继承自HttpApplication类,用于维护一个HttpApplication对象池,并在需要的时候讲对象池中的对象分配给应用程序。

     2.创建一个特殊的HttpApplication对象,并调用它的Application_Start方法。

     3.获取一个用于处理当前请求的HttpApplication实例,进行初始化。

 1 internal static IHttpHandler GetApplicationInstance(HttpContext context)
 2 {
 3     if (_customApplication != null)
 4     {
 5         return _customApplication;
 6     }
 7     if (context.Request.IsDebuggingRequest)
 8     {
 9         return new HttpDebugHandler();
10     }
11     _theApplicationFactory.EnsureInited();
12     _theApplicationFactory.EnsureAppStartCalled(context);
13     return _theApplicationFactory.GetNormalApplicationInstance(context);
14 }
View Code

      初始化:①.创建HttpModuleCollection集合——>根据配置文件,获取所有的HttpModule,并循环执行HttpModule的初始化方法。

 

 1 private void InitModules()
 2 {
 3     HttpModuleCollection modules = RuntimeConfig.GetAppConfig().HttpModules.CreateModules();
 4     HttpModuleCollection other = this.CreateDynamicModules();
 5     modules.AppendCollection(other);
 6     this._moduleCollection = modules;
 7     this.InitModulesCommon();
 8 }
 9 
10  
11 private void InitModulesCommon()
12 {
13     int count = this._moduleCollection.Count;
14     for (int i = 0; i < count; i++)
15     {
16         this._currentModuleCollectionKey = this._moduleCollection.GetKey(i);
17         this._moduleCollection[i].Init(this);
18     }
19     this._currentModuleCollectionKey = null;
20     this.InitAppLevelCulture();
21 }
View Code

 

           ②.对HttpApplication的管道事件和HttpHandler有序绑定,主要有两处HttpHandler。

           1.——>在管道第7-8个事件之间执行了MapHandlerExecutionStep事件:
                 判断是否指向了一个具体的HttpHandler实例,如果没有,则根据请求的url创建页面处理程序或一般处理程序。
                (为什么要判断是否指向一个具体的HttpHandler呢,MVC请求到达的时候会在第七个事件中,指向一个MvcHandler,而不是创建一般处理程序)

             2.——>在管道第11-12个事件之间执行了HttpHandler的ProcessRequest方法:
                 执行一般处理程序的ProceRequest方法,或者是Page页面的生命周期。

 

 1 internal override void BuildSteps(WaitCallback stepCallback)
 2 {
 3     ArrayList steps = new ArrayList();
 4     HttpApplication app = base._application;
 5     bool flag = false;
 6     UrlMappingsSection urlMappings = RuntimeConfig.GetConfig().UrlMappings;
 7     flag = urlMappings.IsEnabled && (urlMappings.UrlMappings.Count > 0);
 8     steps.Add(new HttpApplication.ValidateRequestExecutionStep(app));
 9     steps.Add(new HttpApplication.ValidatePathExecutionStep(app));
10     if (flag)
11     {
12         steps.Add(new HttpApplication.UrlMappingsExecutionStep(app));
13     }
14     app.CreateEventExecutionSteps(HttpApplication.EventBeginRequest, steps);
15     app.CreateEventExecutionSteps(HttpApplication.EventAuthenticateRequest, steps);
16     app.CreateEventExecutionSteps(HttpApplication.EventDefaultAuthentication, steps);
17     app.CreateEventExecutionSteps(HttpApplication.EventPostAuthenticateRequest, steps);
18     app.CreateEventExecutionSteps(HttpApplication.EventAuthorizeRequest, steps);
19     app.CreateEventExecutionSteps(HttpApplication.EventPostAuthorizeRequest, steps);
20     app.CreateEventExecutionSteps(HttpApplication.EventResolveRequestCache, steps);
21     app.CreateEventExecutionSteps(HttpApplication.EventPostResolveRequestCache, steps);
22     
23     //创建页面对象或一般处理程序
24     steps.Add(new HttpApplication.MapHandlerExecutionStep(app));
25     app.CreateEventExecutionSteps(HttpApplication.EventPostMapRequestHandler, steps);
26     app.CreateEventExecutionSteps(HttpApplication.EventAcquireRequestState, steps);
27     app.CreateEventExecutionSteps(HttpApplication.EventPostAcquireRequestState, steps);
28     app.CreateEventExecutionSteps(HttpApplication.EventPreRequestHandlerExecute, steps);
29     steps.Add(app.CreateImplicitAsyncPreloadExecutionStep());
30 
31     //执行一般处理程序的PR方法或开始Page页面的生命周期
32     steps.Add(new HttpApplication.CallHandlerExecutionStep(app));
33     app.CreateEventExecutionSteps(HttpApplication.EventPostRequestHandlerExecute, steps);
34     app.CreateEventExecutionSteps(HttpApplication.EventReleaseRequestState, steps);
35     app.CreateEventExecutionSteps(HttpApplication.EventPostReleaseRequestState, steps);
36     steps.Add(new HttpApplication.CallFilterExecutionStep(app));
37     app.CreateEventExecutionSteps(HttpApplication.EventUpdateRequestCache, steps);
38     app.CreateEventExecutionSteps(HttpApplication.EventPostUpdateRequestCache, steps);
39     this._endRequestStepIndex = steps.Count;
40     app.CreateEventExecutionSteps(HttpApplication.EventEndRequest, steps);
41     steps.Add(new HttpApplication.NoopExecutionStep());
42     this._execSteps = new HttpApplication.IExecutionStep[steps.Count];
43     steps.CopyTo(this._execSteps);
44     this._resumeStepsWaitCallback = stepCallback;
45 }
View Code

HttpRuntime拿到了HttpApplication对象,HttpRuntime开始触发HttpApplication的请求处理,即调用HttpApplication的BeginProcessRequest方法。

 1 IAsyncResult IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
 2 {
 3     this._context = context;
 4     this._context.ApplicationInstance = this;
 5     this._stepManager.InitRequest();
 6     this._context.Root();
 7     HttpAsyncResult result = new HttpAsyncResult(cb, extraData);
 8     this.AsyncResult = result;
 9     if (this._context.TraceIsEnabled)
10     {
11         HttpRuntime.Profile.StartRequest(this._context);
12     }
13     this.ResumeSteps(null);
14     return result;
15 }
16 
17  
View Code

ResumeSteps  

  其中error = application.ExecuteStep(this._execSteps[this._currentStepIndex], ref completedSynchronously);

  便是通过_execSteps来依次执行事件函数的调用。

  在所有事件函数被调用完成之后,HttpApplication实例会被回收,ISAPIRuntime.ProcessRequest处理完毕,结果返回给COM,并通过COM的再一次处理,返回给客户端。这样一次请求就至此结束了。

  1 [DebuggerStepperBoundary]
  2 internal override void ResumeSteps(Exception error)
  3 {
  4     bool flag = false;
  5     bool completedSynchronously = true;
  6     HttpApplication application = base._application;
  7     CountdownTask applicationInstanceConsumersCounter = application.ApplicationInstanceConsumersCounter;
  8     HttpContext context = application.Context;
  9     ThreadContext context2 = null;
 10     AspNetSynchronizationContextBase syncContext = context.SyncContext;
 11     try
 12     {
 13         if (applicationInstanceConsumersCounter != null)
 14         {
 15             applicationInstanceConsumersCounter.MarkOperationPending();
 16         }
 17         using (syncContext.AcquireThreadLock())
 18         {
 19             try
 20             {
 21                 context2 = application.OnThreadEnter();
 22             }
 23             catch (Exception exception)
 24             {
 25                 if (error == null)
 26                 {
 27                     error = exception;
 28                 }
 29             }
 30             try
 31             {
 32                 try
 33                 {
 34                 Label_004D:
 35                     if (syncContext.Error != null)
 36                     {
 37                         error = syncContext.Error;
 38                         syncContext.ClearError();
 39                     }
 40                     if (error != null)
 41                     {
 42                         application.RecordError(error);
 43                         error = null;
 44                     }
 45                     if (!syncContext.PendingCompletion(this._resumeStepsWaitCallback))
 46                     {
 47                         if ((this._currentStepIndex < this._endRequestStepIndex) && ((context.Error != null) || base._requestCompleted))
 48                         {
 49                             context.Response.FilterOutput();
 50                             this._currentStepIndex = this._endRequestStepIndex;
 51                         }
 52                         else
 53                         {
 54                             this._currentStepIndex++;
 55                         }
 56                         if (this._currentStepIndex >= this._execSteps.Length)
 57                         {
 58                             flag = true;
 59                         }
 60                         else
 61                         {
 62                             this._numStepCalls++;
 63                             syncContext.Enable();
 64                             error = application.ExecuteStep(this._execSteps[this._currentStepIndex], ref completedSynchronously);
 65                             if (completedSynchronously)
 66                             {
 67                                 this._numSyncStepCalls++;
 68                                 goto Label_004D;
 69                             }
 70                         }
 71                     }
 72                 }
 73                 finally
 74                 {
 75                     if (flag)
 76                     {
 77                         context.RaiseOnRequestCompleted();
 78                     }
 79                     if (context2 != null)
 80                     {
 81                         try
 82                         {
 83                             context2.DisassociateFromCurrentThread();
 84                         }
 85                         catch
 86                         {
 87                         }
 88                     }
 89                 }
 90             }
 91             catch
 92             {
 93                 throw;
 94             }
 95         }
 96         if (flag)
 97         {
 98             context.RaiseOnPipelineCompleted();
 99             context.Unroot();
100             application.AsyncResult.Complete(this._numStepCalls == this._numSyncStepCalls, null, null);
101             application.ReleaseAppInstance();
102         }
103     }
104     finally
105     {
106         if (applicationInstanceConsumersCounter != null)
107         {
108             applicationInstanceConsumersCounter.MarkOperationCompleted();
109         }
110     }
111 }
View Code

HttpApplication 管线会依次处理下面的请求:

  1. 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。
  2. 如果已在 Web.config 文件的 UrlMappingsSection 节中配置了任何 URL,则执行 URL 映射。
  3. 引发 BeginRequest 事件。
  4. 引发 AuthenticateRequest 事件。
  5. 引发 PostAuthenticateRequest 事件。
  6. 引发 AuthorizeRequest 事件。
  7. 引发 PostAuthorizeRequest 事件。
  8. 引发 ResolveRequestCache 事件。
  9. 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。
  10. 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)
  11. 引发 PostMapRequestHandler 事件。继续通知HttpModule确定要使用哪个HttpHandler用以处理请求。
  12. 引发 AcquireRequestState 事件。
  13. 引发 PostAcquireRequestState 事件。
  14. 引发 PreRequestHandlerExecute 事件。
  15. 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。
  16. 引发 PostRequestHandlerExecute 事件。
  17. 引发 ReleaseRequestState 事件。
  18. 引发 PostReleaseRequestState 事件。
  19. 如果定义了 Filter 属性,则执行响应筛选。
  20. 引发 UpdateRequestCache 事件。
  21. 引发 PostUpdateRequestCache 事件。
  22. 引发 EndRequest 事件。
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