IHttpEventProvider Interface

Article
05/24/2022

Provides a generic event-reporting interface.

Syntax

class IHttpEventProvider

Methods

The following table lists the methods exposed by the IHttpEventProvider class.

Name	Description
SetErrorStatus	Specifies an error to return.

Derived Classes

The following table lists the derived classes exposed by the IHttpEventProvider interface.

Name	Description
IAuthenticationProvider	Provides an interface for RQ_REQUEST_AUTHENTICATE event notifications.
ICacheProvider	Provides an interface for GL_CACHE_OPERATION event notifications.
ICustomNotificationProvider	Provides an interface for GL_CUSTOM_NOTIFCATION and RQ_CUSTOM_NOTIFCATION event notifications.
IGlobalConfigurationChangeProvider	Provides an interface for GL_CONFIGURATION_CHANGE event notifications.
IGlobalFileChangeProvider	Provides an interface for GL_FILE_CHANGE event notifications.
IGlobalRSCAQueryProvider	Provides an interface for GL_RSCA_QUERY event notifications.
IGlobalStopListeningProvider	Provides an interface for GL_STOP_LISTENING event notifications.
IGlobalThreadCleanupProvider	Provides an interface for GL_THREAD_CLEANUP event notifications.
IGlobalTraceEventProvider	Provides an interface for GL_TRACE_EVENT event notifications.
IHttpApplicationProvider	Provides an interface for GL_APPLICATION_START event notifications.
IMapHandlerProvider	Provides an interface for RQ_DETERMINE_HANDLER event notifications.
IMapPathProvider	Provides an interface for RQ_MAP_PATH event notifications.
IPreBeginRequestProvider	Provides an interface for GL_PRE_BEGIN_REQUEST event notifications.
IReadEntityProvider	Provides an interface for RQ_READ_ENTITY event notifications.
ISendResponseProvider	Provides an interface for RQ_SEND_RESPONSE event notifications.

Remarks

The IHttpEventProvider interface provides the generic event-reporting interface for most notification methods, and it serves as the parent class for the event-reporting interfaces that are used with the remaining notifications.

The IHttpEventProvider interface exposes only the SetErrorStatus method, which sets the error status for the current context. Several of the derived classes that are inherited from IHttpEventProvider expose additional methods that are specific to their respective events.

Example

The following code example demonstrates how to create an HTTP module that sends an example string to the Web client and captures the return value from this operation. The module uses the SetErrorStatus method to specify the return value as the error status for the current request and then exits.

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

// Create the module class.
class MyHttpModule : public CHttpModule
{
public:
    REQUEST_NOTIFICATION_STATUS
    OnBeginRequest(
        IN IHttpContext * pHttpContext,
        IN IHttpEventProvider * pProvider
    )
    {
        // Create an HRESULT to receive return values from methods.
        HRESULT hr;

        // Clear the existing response.
        pHttpContext->GetResponse()->Clear();
        // Set the MIME type to plain text.
        pHttpContext->GetResponse()->SetHeader(
            HttpHeaderContentType,"text/plain",
            (USHORT)strlen("text/plain"),TRUE);

        // Return a simple message to the Web client.
        hr = WriteResponseMessage(pHttpContext,"Hello World!");

        // Set the error status for the module.
        pProvider->SetErrorStatus( hr );

        // End additional processing.
        return RQ_NOTIFICATION_FINISH_REQUEST;
    }

private:

    // Create a utility method that inserts a string value into the response.
    HRESULT WriteResponseMessage(
        IHttpContext * pHttpContext,
        PCSTR pszBuffer
    )
    {
        // Create an HRESULT to receive return values from methods.
        HRESULT hr;
        
        // Create a data chunk.
        HTTP_DATA_CHUNK dataChunk;
        // Set the chunk to a chunk in memory.
        dataChunk.DataChunkType = HttpDataChunkFromMemory;
        // Buffer for bytes written of data chunk.
        DWORD cbSent;

        // Set the chunk to the buffer.
        dataChunk.FromMemory.pBuffer =
            (PVOID) pszBuffer;
        // Set the chunk size to the buffer size.
        dataChunk.FromMemory.BufferLength =
            (USHORT) strlen(pszBuffer);
        // Insert the data chunk into the response.
        hr = pHttpContext->GetResponse()->WriteEntityChunks(
            &dataChunk,1,FALSE,TRUE,&cbSent);
        // Test for an error.
        if (FAILED(hr))
        {
            // Return the error status.
            return hr;
        }

        // Return a success status.
        return S_OK;
    }
};

// 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(
        new MyHttpModuleFactory,
        RQ_BEGIN_REQUEST,
        0
    );
}

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

Type	Description
Client	- IIS 7.0 on Windows Vista - IIS 7.5 on Windows 7 - IIS 8.0 on Windows 8 - IIS 10.0 on Windows 10
Server	- IIS 7.0 on Windows Server 2008 - IIS 7.5 on Windows Server 2008 R2 - IIS 8.0 on Windows Server 2012 - IIS 8.5 on Windows Server 2012 R2 - IIS 10.0 on Windows Server 2016
Product	- IIS 7.0, IIS 7.5, IIS 8.0, IIS 8.5, IIS 10.0 - IIS Express 7.5, IIS Express 8.0, IIS Express 10.0
Header	Httpserv.h

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