IHttpContext::NotifyCustomNotification Method

Article
05/20/2022

Raises a custom request-level notification.

Syntax

virtual HRESULT NotifyCustomNotification(  
   ICustomNotificationProvider* pCustomOutput,  
   BOOL* pfCompletionExpected  
) = 0;

Parameters

pCustomOutput
A pointer to an ICustomNotificationProvider.

pfCompletionExpected
true if asynchronous completion is expected; otherwise, false.

Return Value

An HRESULT. Possible values include, but are not limited to, those in the following table.

Value	Description
S_OK	Indicates that the operation was successful.
ERROR_NOT_ENOUGH_MEMORY	Indicates that there is insufficient memory to perform the operation.

Remarks

The NotifyCustomNotification method raises the custom notification that is specified by the ICustomNotificationProvider interface in the pCustomOutput parameter.

Your module must register for the RQ_CUSTOM_NOTIFICATION notification, and your module must contain a CHttpModule::OnCustomRequestNotification method to process the custom notification. To raise the custom notification, your module must first create the instance of your custom ICustomNotificationProvider interface and pass that interface to the NotifyCustomNotification method for the current request context.

Example

The following code example demonstrates how to create an HTTP module that performs the following tasks:

Registers for the RQ_BEGIN_REQUEST and RQ_CUSTOM_NOTIFICATION notifications.
Creates a CHttpModule class that contains OnBeginRequest and OnCustomRequestNotification methods.
1. The OnBeginRequest method writes to the Event Viewer an event that specifies the current notification. The method then creates an instance of an ICustomNotificationProvider interface and raises the custom notification by using the NotifyCustomNotification method.
2. The OnCustomRequestNotification method uses the ICustomNotificationProvider::QueryNotificationType method to retrieve the unique identifier for the custom notification. If the unique identifier matches, the OnCustomRequestNotification method writes to the Event Viewer an event that specifies that the custom notification was raised.
Removes the CHttpModule class from memory and then exits.

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

// Define the unique notification indentifier.
#define MY_CUSTOM_NOTIFICATION L"MyCustomNotification"

// Create the custom notification class.
class MyCustomProvider : public ICustomNotificationProvider
{
public:
    // Create the method that will identify the custom notification.
    PCWSTR QueryNotificationType(VOID)
    {
        // Return the unique identifier string for the custom notification.
        return MY_CUSTOM_NOTIFICATION;
    }
    // Create the method that will process errors.
    VOID SetErrorStatus(HRESULT hrError)
    {
        return;
    }
};

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

    // Create a handle for the Event Viewer.
    HANDLE m_hEventLog;
    // Create a pointer for the custom notification.
    MyCustomProvider * m_pCustomProvider;

public:

    MyHttpModule()
    {
        // Open the global handle to the Event Viewer.
        m_hEventLog = RegisterEventSource( NULL,"IISADMIN" );
        // Initialize the pointer for the custom notification to NULL.
        m_pCustomProvider = NULL;
    }

    ~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;
        }
        // Test whether the pointer for the custom notification is valid.
        if (NULL != m_pCustomProvider)
        {
            // Remove the custom notification from memory.
            delete m_pCustomProvider;
            m_pCustomProvider = NULL;
        }
    }

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

        // Create an array of strings.
        LPCSTR szBuffer[2] = {"MyHttpModule","OnBeginRequest"};
        // Write the strings to the Event Viewer.
        WriteEventViewerLog(szBuffer,2);

        // Create the custom notification provider class.
        MyCustomProvider * m_pCustomProvider = new MyCustomProvider;

        // Test if the custom notification pointer is valid.
        if (NULL != m_pCustomProvider)
        {
            // Raise the custom notification.
            BOOL fCompletionExpected = TRUE;
            pHttpContext->NotifyCustomNotification(m_pCustomProvider, &fCompletionExpected);
        }

        // Return processing to the pipeline.
        return RQ_NOTIFICATION_CONTINUE;
    }

    REQUEST_NOTIFICATION_STATUS
    OnCustomRequestNotification(
        IN IHttpContext * pHttpContext,
        IN ICustomNotificationProvider * pProvider
    )
    {
        UNREFERENCED_PARAMETER( pHttpContext );

        // Retrieve the custom notification type;
        PCWSTR pNotificationType = pProvider->QueryNotificationType();

        if (0 == wcscmp(pNotificationType,MY_CUSTOM_NOTIFICATION))
        {
            // Create an array of strings.
            LPCSTR szBuffer[2] = {"MyHttpModule","OnCustomRequestNotification"};
            // Write the strings to the Event Viewer.
            WriteEventViewerLog(szBuffer,2);
        }

        // Return processing to the pipeline.
        return RQ_NOTIFICATION_CONTINUE;
    }

private:

    // Create a method that writes to the Event Viewer.
    BOOL WriteEventViewerLog(LPCSTR szBuffer[], WORD wNumStrings)
    {
        // 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, wNumStrings,
                0, szBuffer, 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 );

    // Create an HRESULT to receive return values from methods.
    HRESULT hr;

    // Set the request notifications.
    hr = pModuleInfo->SetRequestNotifications(
        new MyHttpModuleFactory,
        RQ_BEGIN_REQUEST | RQ_CUSTOM_NOTIFICATION, 0 );

    // Test for an error and exit if necessary.
    if (FAILED(hr))
    {
        return hr;
    }

    // Return a success status;
    return S_OK;
}

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