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IHttpFileInfo::GetModuleContextContainer Method

IIS 7.0

Returns an IHttpModuleContextContainer pointer for the corresponding file.

virtual IHttpModuleContextContainer* GetModuleContextContainer(
   VOID
) = 0;

This method takes no parameters.

A pointer to an IHttpModuleContextContainer interface.

The GetModuleContextContainer method return value depends on implementation. By default, the current implementation creates an IDispensedHttpModuleContextContainer that is synchronized but not dispensed.

IHttpFileInfo implementers are responsible for memory management with this data; therefore, IHttpFileInfo implementers should create an IDispensedHttpModuleContextContainer pointer at construction and hold a private reference to this IDispensedHttpModuleContextContainer pointer for the life of the IHttpFileInfo pointer. When the GetModuleContextContainer method is called, you should upcast and return this same IDispensedHttpModuleContextContainer pointer. When the destructor of the class that implements the IHttpFileInfo interface is called, this destructor should call the IDispensedHttpModuleContextContainer::ReleaseContainer method on this private reference and then set that reference to NULL.

GetModuleContextContainer should not return NULL. If the internal container is NULL, set this internal container to the value on the call to IHttpServer::DispenseContainer, and then return this same container.

NoteNote:

   Although implicit upcast operations are considered safe, consider using an explicit cast for program clarity. Also consider using the dynamic_cast operator whenever possible.

IHttpFileInfo implementers are responsible for memory management with this data; therefore, IHttpFileInfo clients must not release, call delete on, or attempt to downcast and call IDispensedHttpModuleContextContainer::ReleaseContainer on the returned IHttpModuleContextContainer pointer when this data is no longer needed.

The following code example demonstrates a custom class named MyContainer that implements the IDispensedHttpModuleContextContainer interface, and a custom class named MyClass that implements the IHttpFileInfo interface. MyClass manages a MyContainer pointer during the lifetime of a MyClass pointer.

#pragma warning( disable : 4290 )
#pragma warning( disable : 4530 )

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

#include <string>
using namespace std;

// The CConvert class mirrors the Convert class that is 
// defined in the .NET Framework. It converts primitives 
// and other data types to wstring types.
class CConvert
{
public:
    // The ToString method converts a BOOL to a wstring.
    // b: the BOOL value to convert to a wstring.
    // return: L"true" for true; otherwise, L"false" for false.
    static wstring ToString(BOOL b)
    {
        return (b) ? L"true" : L"false";
    }

    // The ToByteString converts a double-byte 
    // character string to a single-byte string.
    // str: the double-byte string to convert.
    // return: a single-byte string copied from str.
    static string ToByteString(const wstring& str)
    {
        // Get the length of the 
        // double-byte string.
        size_t length = str.length();

        // Create a temporary char pointer.
        char* byteChar = new char[length+1];
        byteChar[0] = '\0';
        // Copy the double-byte character string
        // into the single-byte string.        
        size_t charsReturned = 0;
        wcstombs_s(&charsReturned, byteChar, 
                   length+1, str.c_str(), length+1);
        // Create a string to return.
        string retString = byteChar;
        // Delete the temporary string and
        // set that string to NULL.
        delete[] byteChar;
        byteChar = NULL;

        // Return the single-byte string.
        return retString;
    }
};

// The CResponseWriter class writes 
// text to the response stream.
class CResponseWriter
{
public:
    // Creates the CResponseWriter class.
    // response: the IHttpResponse 
    // pointer to write to.
    // throws: a _com_error exception if
    // the IHttpResponse pointer is NULL.
    CResponseWriter(IHttpResponse* response)
        throw (_com_error)
    {
        // If the response is NULL,
        // throw an exception.
        if (NULL == response)
        {
            ThrowOnFail(E_INVALIDARG);            
        }

        // Set the internal response.
        m_response = response;
    }

    // The destructor for the CResponseWriter
    // class. The CResponseWriter method 
    // sets the IHttpResponse pointer to NULL.
    virtual ~CResponseWriter()
    {
        m_response = NULL;
    }

    // The Write method writes the 
    // PCSTR to the response stream.
    // pszValue: the PCSTR to write.
    // throws: a _com_error if the 
    // Write method fails.
    void Write
    (
        PCSTR pszValue        
    ) throw (_com_error)
    {
        // The string must not be 
        // NULL, and its length must 
        // be greater than 0.
        if ((NULL == pszValue) || 
            (strlen(pszValue) < 1))            
        {
            // Throw an invalid argument
            // exception.
            ThrowOnFail(E_INVALIDARG);                        
        }        

        // Create a data chunk structure.
        HTTP_DATA_CHUNK dataChunk;
        // Set the chunk to a chunk in memory.
        dataChunk.DataChunkType = 
            HttpDataChunkFromMemory;

        // Set the chunk to 
        // the pszValue parameter.
        dataChunk.FromMemory.pBuffer = 
            (PVOID)pszValue;
        // Set the chunk size 
        // to the pszValue length.
        dataChunk.FromMemory.BufferLength = 
            (USHORT)strlen(pszValue);

        // Declare and initialize OUT 
        // parameters for the WriteEntityChunks 
        // method.
        DWORD pcbSent = 0;
        BOOL pfCompletionExpected = FALSE;

        // Write the entity chunks to
        // the response stream.
        HRESULT hr =
            m_response->WriteEntityChunks
                (&dataChunk,
                 1,
                 FALSE,
                 FALSE,
                 &pcbSent,
                 &pfCompletionExpected);

        // Throw an exception if the call
        // to WriteEntityChunks is not a 
        // success.
        ThrowOnFail(hr);        
    }

    // The WriteLine method writes a string
    // and newline characters to the response steam.
    // pszValue: the PCSTR string to write.
    // throws: a _com_error if the PCSTR 
    // or the newline characters are not 
    // written to the response stream.
    void WriteLine
    (
        PCSTR pszValue        
    ) throw (_com_error)
    {
        // Try to write the pszValue parameter.
        Write(pszValue);        

        // Try to write the newline characters.
        Write("\r\n");
    }

    // Convenience method that writes a name 
    // and value pair to the response stream.
    // name: the name of the parameter.
    // value: the value of the parameter.
    // throws: a _com_error exception if
    // the response stream is not written.
    void WriteLine
    (
        const wstring& name,
        const wstring& value
    ) throw (_com_error)
    {
        // Convert the UNICODE strings 
        // to mutlibyte strings.
        string nameMulti = 
            CConvert::ToByteString(name);
        string valueMulti = 
            CConvert::ToByteString(value);

        // Create the string to write.
        string writeString =
            nameMulti + 
            string(":  ") + 
            valueMulti;

        // Write the line to
        // the response stream.
        WriteLine(writeString.c_str());        
    }

    // Tests an HRESULT for success.
    // hr: the HRESULT value to inspect.
    // throws: a _com_error if the HRESULT
    // parameter is not S_OK.
    static void ThrowOnFail(HRESULT hr)
    {
        if (FAILED(hr))
        {
            _com_error ce(hr);
            throw ce;
        }
    }
private:
    // Specify the IHttpResponse
    // pointer to write to.
    IHttpResponse* m_response;
};

// The MyHttpModule class extends the CHttpModule 
// class and handles response processing.  This 
// class handles retrieving an IHttpFileInfo pointer 
// from the IHttpContext pointer during the overridden 
// OnSendResponse method, and writes the IHttpFileInfo 
// data to the response stream.
class MyHttpModule : public CHttpModule
{
public:
    // The MyHttpModule method is the public 
    // constructor for the MyHttpModule class.
    MyHttpModule()
    {

    }

    // The OnSendResponse method 
    // handles respose processing.
    // pHttpContext: an IHttpContext pointer.
    // pProvider: an ISendResponseProvider pointer.
    // return: RQ_NOTIFICATION_FINISH_REQUEST if the 
    // IHttpFileInfo pointer can be retrieved from the 
    // pHttpContext parameter; otherwise, 
    // RQ_NOTIFICATION_CONTINUE.
    REQUEST_NOTIFICATION_STATUS OnSendResponse
    (
        IN IHttpContext* pHttpContext,
        IN OUT ISendResponseProvider* pProvider
    )
    {
        // Use the UNREFERENCED_PARAMETER macro since
        // the pProvider parameter is never used.
        UNREFERENCED_PARAMETER(pProvider);

        if (NULL == pHttpContext)
        {
            return RQ_NOTIFICATION_CONTINUE;
        }

        // Get an IHttpFileInfo pointer 
        // from the IHttpContext pointer.
        IHttpFileInfo* fileInfo = 
            pHttpContext->GetFileInfo();

        // Get the IHttpResponse pointer 
        // from the IHttpContext pointer.
        IHttpResponse* response = 
            pHttpContext->GetResponse();

        // Both the IHttpFileInfo pointer
        // and IHttpResponse pointer are
        // required for processing.
        if ((NULL == fileInfo) ||
            (NULL == response))
        {
            return RQ_NOTIFICATION_CONTINUE;
        }

        // Clear the existing response stream.        
        response->Clear();

        // Set the response header to plain text.
        HRESULT hr = 
            response->SetHeader(HttpHeaderContentType, 
                                "text/plain", 
                                (USHORT)strlen("text/plain"), 
                                 TRUE);

        // If the SetHeader method fails,
        // call the SetStatus with an error code.
        if (FAILED(hr))
        {
            response->SetStatus(500, 
                                "IHttpResponse::SetHeader", 
                                0, hr);
            return RQ_NOTIFICATION_CONTINUE;
        }

        // The CResponseWriter will throw a 
        // com_exception if it cannot be created, 
        // or if the response stream cannot be written. 
        // Create a new CResponseWriter, and wrap 
        // all calls into that CResponseWriter,
        // with a try-catch statement.
        try
        {
            // Declare a writer for 
            // the response stream.
            CResponseWriter writer(response);

            // Get the IHttpModuleContextContainer
            // from the IHttpFileInfo pointer.
            IHttpModuleContextContainer* contextContainer =
                fileInfo->GetModuleContextContainer();        

            // Convert the IHttpModuleContextContainer
            // pointer to a wstring.
            wstring contextString =
                CConvert::ToString(NULL != contextContainer);

            // Write the context data to
            // the response stream.
            writer.WriteLine(L"Context", contextString);
        }
        catch (_com_error& ce)
        {
            // Attempt to get the 
            // description of the error.
            _bstr_t description = 
                ce.Description();

            // Print the description if 
            // it is not empty.
            if (0 == description.length())
            {
                description = ce.ErrorMessage();            
            }

            // Set an error status on the 
            // IHttpResponse pointer.
            response->SetStatus(500, description, 0, ce.Error());            
        }

        // Return RQ_NOTIFICATION_FINISH_REQUEST, which 
        // will terminate any additional request processing.
        return RQ_NOTIFICATION_FINISH_REQUEST;
    }
protected:    
    // The MyHttpModule is the protected virtual
    // constructor for the MyHttpModule class.
    virtual ~MyHttpModule()
    {

    }
};

// The MyHttpModuleFactory class implements the IHttpModuleFactory 
// interface, and creates a new MyHttpModule pointer, where this
// MyHttpModule listens for RQ_SEND_RESPONSE events.
class MyHttpModuleFactory : public IHttpModuleFactory
{
public:
    // The RegisterGlobalModule method creates a new 
    // MyHttpModuleFactory pointer, assigns that pointer 
    // as the factory on the pModuleInfo parameter, and
    // registers for RQ_SEND_RESPONSE events.
    // dwServerVersion: the current server version.
    // pModuleInfo: the IHttpModuleRegistrationInfo 
    // used for requesting notifications.
    // pGlobalInfo: the IHttpServer pointer.
    static HRESULT RegisterGlobalModule
    (
        DWORD dwServerVersion,
        IHttpModuleRegistrationInfo* pModuleInfo,
        IHttpServer* pGlobalInfo
    )
    {
        // Create a new MyHttpModuleFactory pointer.
        MyHttpModuleFactory* factory =
            new MyHttpModuleFactory;

        // If the factory is NULL, return a
        // return a ERROR_NOT_ENOUGH_MEMORY 
        // errror.
        if (NULL == factory)
        {
            return HRESULT_FROM_WIN32(ERROR_NOT_ENOUGH_MEMORY);
        }

        // Return the value from calling the 
        // SetRequestNotifications method by 
        // passing the factory for RQ_SEND_RESPONSE
        // events.
        return pModuleInfo->SetRequestNotifications(
            factory,
            RQ_SEND_RESPONSE,
            0);
    }

    // The GetHttpModule method creates a new MyHttpModule 
    // pointer and sets the ppModule with this pointer.
    // ppModule: the OUT parameter which 
    // accepts a new CHttpModule subclass.
    // pAllocator: the IModuleAllocator pointer, 
    // which is unused in this implementation.
    virtual HRESULT GetHttpModule
    (
        OUT CHttpModule** ppModule, 
        IN IModuleAllocator* pAllocator
    )
    {
        // Call the UNREFERENCED_PARAMETER with 
        // the IModuleAllocator pointer, because
        // this parameter is never used.
        UNREFERENCED_PARAMETER(pAllocator);        

        // Create a new MyHttpModule pointer and assign
        // it to the dereferenced ppModule pointer.
        *ppModule = new MyHttpModule;

        // If the dereferenced ppModule is NULL 
        // then heap memory is exhausted. Return
        // an ERROR_NOT_ENOUGH_MEMORY error.
        if (NULL == *ppModule)
        {
            return HRESULT_FROM_WIN32(ERROR_NOT_ENOUGH_MEMORY);
        }

        // Creating a new MyHttpModule pointer 
        // was successful; return S_OK.
        return S_OK;       
    }

    // The Terminate method must be implemented
    // by IHttpModuleFactory implementers, 
    // and calls delete on this.
    virtual void Terminate()
    {
        delete this;
    }

private:
    // The MyHttpModuleFactory is the 
    // protected constructor for the 
    // MyHttpModuleFactory class.
    MyHttpModuleFactory()
    {

    }

    // The MyHttpModuleFactory method is the 
    // protected virtual destructor for the 
    // MyHttpModuleFactory class.
    virtual ~MyHttpModuleFactory()
    {

    }
};

// The RegisterModule method is the 
// main entry point for the DLL.
// dwServerVersion: the current server version.
// pModuleInfo: the current 
// IHttpModuleRegistrationInfo pointer.
// pGlobalInfo: the current IHttpServer pointer.
// return: the HRESULT value returned from 
// the MyHttpModuleFactory::RegisterGlobalModule
// static method.
HRESULT
__stdcall
RegisterModule
(
    DWORD dwServerVersion,
    IHttpModuleRegistrationInfo* pModuleInfo,
    IHttpServer* pGlobalInfo
)
{    
    // Register for global events using the MyHttpModuleFactory 
    // class' static RegisterGlobalModule method.
    return MyHttpModuleFactory::RegisterGlobalModule
        (dwServerVersion, pModuleInfo, pGlobalInfo);  
}


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.

Type

Description

Client

  • IIS 7.0 on Windows Vista

  • IIS 7.5 on Windows 7

  • IIS Express 7.5 on Windows XP, Windows Vista, Windows 7

  • IIS 8.0 on Windows 8 Client

Server

  • IIS 7.0 on Windows Server 2008

  • IIS 7.5 on Windows Server 2008 R2

  • IIS Express 7.5 on Windows Server 2003, Windows Server 2008, Windows Server 2008 R2

  • IIS 8.0 on Windows Server 2012

Product

IIS 7.0, IIS 7.5, IIS Express 7.5, IIS 8.0

Header

Httpserv.h

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