HTTP Whole Message Filter Example

The following diagram illustrates the class relationship between the MHTTPDataOptimiser interface and the RHTTPSession class:

Figure: Class relationship between MHTTPDataOptimiser and RHTTPSession

For more information about MHTTPTransactionCallback, see A simple HTTP Client session.

The following code segment illustrates how to define the header file required for implementing the HTTP Whole Message Filter APIs:

#include <http.h>

class CMyHTTPClient: public CBase,
                    public MHTTPTransactionCallback,
                    public MHttpDataOptimiser
public: // methods from MHTTPTransactionCallback
    virtual void MHFRunL(RHTTPTransaction aTransaction, const THTTPEvent& aEvent);
    virtual TInt MHFRunError(TInt aError, RHTTPTransaction aTransaction, const THTTPEvent& aEvent);
public: // methods from MHttpDataOptimiser
    virtual void EncodeL (const TDesC8& aHttpData, HBufC8*& aEncodedData);
    virtual void DecodeL (const TDesC8& aData, HBufC8*& aHttpData, TBool& aTransFail);

The following code segment illustrates how HTTP Whole Message Filter APIs can be used to enable support for Web Acceleration:

#include "CMyHTTPClient.h"

//    CMyHTTPClient.cpp
//    defines CMyHTTPClient class: CMyHTTPClient
// Literals used in the file
_LIT8(KHttpAuthenticationUrl,        "");

void CMyHTTPClient::CreateTransactionL()
    TUriParser8 up;

    RHTTPSession session;
    RHTTPTransaction trans;
    // Open the HTTP session

    RStringPool strP = session.StringPool();

  //To enable MHTTPDataOptimiser for transaction

    // Open a GET transaction, specifying this object as the request body data supplier
    trans = session.OpenTransactionL(up, *this, strP.StringF(HTTP::EGET,RHTTPSession::GetTable()));

    CleanupStack::PopAndDestroy(&session); //Closes the session


TInt CMyHTTPClient::MHFRunError(TInt aError, RHTTPTransaction aTransaction, const THTTPEvent& aEvent)
    // Handle Error appropriately

void CMyHTTPClient::MHFRunL(RHTTPTransaction aTransaction, const THTTPEvent& aEvent)
    // Handle events from the framework.
    switch (aEvent.iStatus)
        case KErrHttpOptimiserFailsTrans:
            INFO_PRINTF1(_L("Cancelling/Failing Transaction\n"));
            } break;

    //The following statement is used to eliminate leavescan errors

void CMyHTTPClient::EncodeL (const TDesC8& aHttpData, HBufC8* &aEncodedData)
    //Provide your own custom encoding implementation

void CMyHTTPClient::DecodeL (const TDesC8& aData, HBufC8*& aHttpData, TBool& aTransFail)
    //Provide your own custom decoding implementation

This code enables the MHTTPDataOptimiser for a transaction by using RHTTPTransaction::SetupHTTPDataOptimiser() and also illustrates where custom encoding and decoding mechanisms are implemented.

Note: Alternatively, in this code, you can use the following code segment to enable MHTTPDataOptimiser for a particular session.