ASP.NET——HttpModule

ASP.NET模組——HttpModule[轉]

HttpModule是如何工作的

當一個HTTP請求到達HttpModule時，整個ASP.NET Framework系統還並沒有對這個HTTP請求做任何處理，也就是說此時對於HTTP請求來講，HttpModule是一個HTTP請求的“必經之路”，所以可以在這個HTTP請求傳遞到真正的請求處理中心（HttpHandler）之前附加一些需要的資訊在這個HTTP請求資訊之上，或者針對截獲的這個HTTP請求資訊作一些額外的工作，或者在某些情況下乾脆終止滿足一些條件的HTTP請求，從而可以起到一個Filter過濾器的作用。

樣本1：

 

using System; using System.Collections.Generic; using System.Text; using System.Web; namespace MyHttpModule {     /// <summary>     /// 說明：用來實現自己的HttpModule類。     /// </summary>     public class MyFirstHttpModule : IHttpModule     {         private void Application_BeginRequest(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             HttpContext context = application.Context;             HttpRequest request = application.Request;             HttpResponse response = application.Response;             response.Write("我來自自訂HttpModule中的BeginRequest<br />");         }         private void Application_EndRequest(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             HttpContext context = application.Context;             HttpRequest request = application.Request;             HttpResponse response = application.Response;             response.Write("我來自自訂HttpModule中的EndRequest<br />");         }         #region IHttpModule 成員         public void Dispose()         {         }           public void Init(HttpApplication application)         {             application.BeginRequest += new EventHandler(Application_BeginRequest);             application.EndRequest += new EventHandler(Application_EndRequest);         }         #endregion     } }

 

在Web.config進行如下配置

<add name="MyFirstHttpModule" type="MyHttpModule.MyFirstHttpModule,MyHttpModule"/>

深入瞭解HttpModule

一個HTTP請求在HttpModule容器的傳遞過程中，會在某一時刻（ResolveRequestCache事件）將這個HTTP請求傳遞給HttpHandler容器。在這個事件之後，HttpModule容器會建立一個HttpHandler的入口執行個體，但是此時並沒有將HTTP請求控制權交出，而是繼續觸發AcquireRequestState事件以及PreRequestHandlerExcute事件。在PreRequestHandlerExcute事件之後，HttpModule視窗就會將控制權暫時交給HttpHandler容器，以便進行真正的HTTP請求處理工作。

而在HttpHandler容器內部會執行ProcessRequest方法來處理HTTP請求。在容器HttpHandler處理完畢整個HTTP請求之後，會將控制權交還給HttpModule，HttpModule則會繼續對處理完畢的HTTP請求資訊流進行層層的轉交動作，直到返回到用戶端為止。

圖1：HttpModule生命週期

樣本2：驗證HttpModule生命週期

 

using System; using System.Collections.Generic; using System.Text; using System.Web; namespace MyHttpModule {     public class ValidaterHttpModule : IHttpModule     {         #region IHttpModule 成員         public void Dispose()         { }         public void Init(HttpApplication application)         {             application.BeginRequest += new EventHandler(application_BeginRequest);             application.EndRequest += new EventHandler(application_EndRequest);             application.PreRequestHandlerExecute += new EventHandler(application_PreRequestHandlerExecute);             application.PostRequestHandlerExecute += new EventHandler(application_PostRequestHandlerExecute);             application.ReleaseRequestState += new EventHandler(application_ReleaseRequestState);             application.AcquireRequestState += new EventHandler(application_AcquireRequestState);             application.AuthenticateRequest += new EventHandler(application_AuthenticateRequest);             application.AuthorizeRequest += new EventHandler(application_AuthorizeRequest);             application.ResolveRequestCache += new EventHandler(application_ResolveRequestCache);             application.PreSendRequestHeaders += new EventHandler(application_PreSendRequestHeaders);             application.PreSendRequestContent += new EventHandler(application_PreSendRequestContent);         }         void application_PreSendRequestContent(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             application.Context.Response.Write("application_PreSendRequestContent<br/>");         }         void application_PreSendRequestHeaders(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             application.Context.Response.Write("application_PreSendRequestHeaders<br/>");         }         void application_ResolveRequestCache(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             application.Context.Response.Write("application_ResolveRequestCache<br/>");         }         void application_AuthorizeRequest(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             application.Context.Response.Write("application_AuthorizeRequest<br/>");         }         void application_AuthenticateRequest(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             application.Context.Response.Write("application_AuthenticateRequest<br/>");         }         void application_AcquireRequestState(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             application.Context.Response.Write("application_AcquireRequestState<br/>");         }         void application_ReleaseRequestState(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             application.Context.Response.Write("application_ReleaseRequestState<br/>");         }         void application_PostRequestHandlerExecute(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             application.Context.Response.Write("application_PostRequestHandlerExecute<br/>");         }         void application_PreRequestHandlerExecute(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             application.Context.Response.Write("application_PreRequestHandlerExecute<br/>");         }         void application_EndRequest(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             application.Context.Response.Write("application_EndRequest<br/>");         }         void application_BeginRequest(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             application.Context.Response.Write("application_BeginRequest<br/>");         }         #endregion     } }

 

多個自訂的Http Module的運作

從運行結果可以看到，在web.config檔案中引入自訂HttpModule的順序就決定了多個自訂HttpModule在處理一個HTTP請求的接管順序。註：系統預設那幾個HttpModule是最先衩ASP.NET Framework所載入上去的。

樣本3：（代碼類同樣本2）

在HttpModule中終止此次的HTTP請求

可以利用HttpModule通過調用HttpApplication.CompleteRequest()方法實現當滿足某一個條件時終止此次的HTTP請求。

需要注意的是，即使調用了HttpApplication.CompleteRequest()方法終止了一個HTTP請求，ASP.NET Framework仍然會觸發HttpApplication後面的這3個事件：EndRequest事件、PreSendRequestHeaders事件、PreSendRequestContent事件。

如果存在多個自訂的HttpModule的話，當Module1終止了一個HTTP請求，這個HTTP請求將不會再觸發Module2中相應的事件了，但Module2的最後三個事件仍會被觸發。

樣本4：

 

using System; using System.Collections.Generic; using System.Text; using System.Web; namespace MyHttpModule {     public class CompleteRequestHttpModule : IHttpModule     {         #region IHttpModule 成員         public void Dispose()         { }         public void Init(HttpApplication application)         {             application.BeginRequest += new EventHandler(Application_BeginRequest);         }         void Application_BeginRequest(object sender, EventArgs e)         {             HttpApplication application = (HttpApplication) sender;             application.CompleteRequest();             application.Context.Response.Write("請求被終止。");         }         #endregion     } }