CHttpModule::OnBeginRequest Method

Represents the method that will handle a BeginRequest event, which occurs as the first event in the HTTP integrated request-processing pipeline for the current request.

Syntax

virtual REQUEST_NOTIFICATION_STATUS OnBeginRequest(  
   IN IHttpContext* pHttpContext,  
   IN IHttpEventProvider* pProvider  
);  

Parameters

pHttpContext
[IN] A pointer to an IHttpContext interface.

pProvider
[IN] A pointer to an IHttpEventProvider interface.

Return Value

A REQUEST_NOTIFICATION_STATUS value.

Remarks

When a request-level module is registered for the RQ_BEGIN_REQUEST event notification, IIS will call the module's OnBeginRequest method when a request enters the integrated request-processing pipeline.

IIS calls a module's OnBeginRequest method before authentication and authorization; this allows developers to use the OnBeginRequest method to process requests where the client's identity is not an issue.

Example

The following example demonstrates how to create a request-level HTTP module that registers for the RQ_BEGIN_REQUEST event and post-event notifications. When a request enters the pipeline, IIS will call the example module's OnBeginRequest and OnPostBeginRequest methods. Each method will write an entry in the application log of the Windows Event Viewer. When processing is complete, the module will exit.

#define _WINSOCKAPI_
#include <windows.h>
#include <sal.h>
#include <httpserv.h>

// Create the module class.
class MyHttpModule : public CHttpModule
{
public:

    // Process an RQ_BEGIN_REQUEST event.
    REQUEST_NOTIFICATION_STATUS
    OnBeginRequest(
        IN IHttpContext * pHttpContext,
        IN IHttpEventProvider * pProvider
    )
    {
        UNREFERENCED_PARAMETER( pHttpContext );
        UNREFERENCED_PARAMETER( pProvider );
        WriteEventViewerLog("OnBeginRequest");
        return RQ_NOTIFICATION_CONTINUE;
    }

    // Process an RQ_BEGIN_REQUEST post-event.
    REQUEST_NOTIFICATION_STATUS
    OnPostBeginRequest(
        IN IHttpContext * pHttpContext,
        IN IHttpEventProvider * pProvider
    )
    {
        UNREFERENCED_PARAMETER( pHttpContext );
        UNREFERENCED_PARAMETER( pProvider );
        WriteEventViewerLog("OnPostBeginRequest");
        return RQ_NOTIFICATION_CONTINUE;
    }

    MyHttpModule()
    {
        // Open a handle to the Event Viewer.
        m_hEventLog = RegisterEventSource( NULL,"IISADMIN" );
    }

    ~MyHttpModule()
    {
        // Test whether the handle for the Event Viewer is open.
        if (NULL != m_hEventLog)
        {
            // Close the handle to the Event Viewer.
            DeregisterEventSource( m_hEventLog );
            m_hEventLog = NULL;
        }
    }

private:

    // Create a handle for the event viewer.
    HANDLE m_hEventLog;

    // Define a method that writes to the Event Viewer.
    BOOL WriteEventViewerLog(LPCSTR szNotification)
    {
        // Test whether the handle for the Event Viewer is open.
        if (NULL != m_hEventLog)
        {
            // Write any strings to the Event Viewer and return.
            return ReportEvent(
                m_hEventLog,
                EVENTLOG_INFORMATION_TYPE, 0, 0,
                NULL, 1, 0, &szNotification, NULL );
        }
        return FALSE;
    }
};

// Create the module's class factory.
class MyHttpModuleFactory : public IHttpModuleFactory
{
public:
    HRESULT
    GetHttpModule(
        OUT CHttpModule ** ppModule, 
        IN IModuleAllocator * pAllocator
    )
    {
        UNREFERENCED_PARAMETER( pAllocator );

        // Create a new instance.
        MyHttpModule * pModule = new MyHttpModule;

        // Test for an error.
        if (!pModule)
        {
            // Return an error if the factory cannot create the instance.
            return HRESULT_FROM_WIN32( ERROR_NOT_ENOUGH_MEMORY );
        }
        else
        {
            // Return a pointer to the module.
            *ppModule = pModule;
            pModule = NULL;
            // Return a success status.
            return S_OK;
        }            
    }

    void Terminate()
    {
        // Remove the class from memory.
        delete this;
    }
};

// Create the module's exported registration function.
HRESULT
__stdcall
RegisterModule(
    DWORD dwServerVersion,
    IHttpModuleRegistrationInfo * pModuleInfo,
    IHttpServer * pGlobalInfo
)
{
    UNREFERENCED_PARAMETER( dwServerVersion );
    UNREFERENCED_PARAMETER( pGlobalInfo );

    // Set the request notifications and exit.
    return pModuleInfo->SetRequestNotifications(
        // Specify the class factory.
        new MyHttpModuleFactory,
        // Specify the event notifications.
        RQ_BEGIN_REQUEST,
        // Specify the post-event notifications.
        RQ_BEGIN_REQUEST
    );
}

Your module must export the RegisterModule function. You can export this function by creating a module definition (.def) file for your project, or you can compile the module by using the /EXPORT:RegisterModule switch. For more information, see Walkthrough: Creating a Request-Level HTTP Module By Using Native Code.

You can optionally compile the code by using the __stdcall (/Gz) calling convention instead of explicitly declaring the calling convention for each function.

Requirements

See Also

CHttpModule Class
CHttpModule::OnPostBeginRequest Method