TStreamAdapter, ADO.Recordset

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3 total messages Started by Dmitry Konnov Thu, 06 Jul 2006 10:04

#304

Author: Dmitry Konnov
Date: Thu, 06 Jul 2006 10:04

10 lines
1088 bytes

Hello,

if somebody kows how to read data from
TADODataset.Recordset into TStreamAdapter and backward
please give me some example code.


Thank you.

Dmitry

Re: TStreamAdapter, ADO.Recordset

#305

Author: Mark Guerrieri
Date: Fri, 07 Jul 2006 14:08

146 lines
4938 bytes

> if somebody kows how to read data from
> TADODataset.Recordset into TStreamAdapter and backward
> please give me some example code.
>

Following are excerpts from an inproc COM server DLL I wrote to convert 
between Recordsets and XML using streams.  You can use the parts that are 
relavant to you...

This code assumes you have imported the ADO library, creating the unit 
ADODB_TLB.CPP:


#include "AdoDb_TLB.H"
#include <memory>

typedef std::auto_ptr<TStreamAdapter> TStreamAdapterPtr;
typedef std::auto_ptr<TStringStream> TStringStreamPtr;
//---------------------------------------------------------------------------

STDMETHODIMP TRsXmlConvertImpl::RsToXml(LPDISPATCH oRs, BSTR* cXml)
{
  HRESULT hResult = S_OK;

  IDispatchPtr pDisp(oRs, true);

  try
  {
    *cXml = 0;

    if(!pDisp.IsBound())
      return E_NOINTERFACE;

    StreamPtr pStream = CoStream::Create();

    TVariant  v;
    IUnknownPtr iunk;
    OLECHECK(pStream->QueryInterface(IID_IUnknown, (LPVOID*)&iunk));
    if(!iunk.IsBound())
      throw Exception("Stream interface does not implement the IUnknown 
interface");

    v = (IUnknown*)iunk;

    _RecordsetPtr rs;
    OLECHECK(pDisp->QueryInterface(Adodb_tlb::IID__Recordset, 
(LPVOID*)&rs));
    if(!rs.IsBound())
      throw Exception("Object does not implement the IRecordset interface");
    OLECHECK(rs->Save(v, adPersistXML));

    WideString wStream;
    OLECHECK(pStream->ReadText(-1, &wStream));
    *cXml = wStream.Detach();
  }
  catch(Exception& e)
  {
     hResult = Error(e.Message.c_str(), IID_IRsXmlConvert, E_FAIL);
  }
  catch(...)
  {
     hResult = Error(_T("Catastrophic error: internal crash"), 
IID_IRsXmlConvert, E_UNEXPECTED);
  }
  return hResult;
}
//---------------------------------------------------------------------------

STDMETHODIMP TRsXmlConvertImpl::XmlToRs(BSTR cXml, LPDISPATCH* oRs)
{
  HRESULT hResult = S_OK;

  try
  {
    if(*oRs != NULL)
      (*oRs)->Release();

    *oRs = NULL;

    if(cXml == 0)
      throw Exception("Recordset cannot be created from an empty XML 
document");

    AnsiString strXml = AnsiString(cXml);

    TStringStreamPtr pStream(new TStringStream(AnsiString(cXml)));
    if(!pStream.get())
      throw Exception("Could not create Stream object");

    pStream->Seek(0, soFromBeginning);

    TStreamAdapterPtr sa(new TStreamAdapter(pStream.get(), soReference));
    if(!sa.get())
      throw Exception("Could not create Stream interface");

    IUnknownPtr iunk;
    OLECHECK(sa->QueryInterface(IID_IUnknown, (LPVOID*)&iunk));
    if(!iunk.IsBound())
      throw Exception("Stream interface does not implement the IUnknown 
interface");

    sa.release();

    _RecordsetPtr oNewRs;

    OLECHECK(CoCreateInstance(CLSID_Recordset, NULL,
          CLSCTX_INPROC_SERVER|CLSCTX_LOCAL_SERVER,
          Adodb_tlb::IID__Recordset, (LPVOID*)&oNewRs));
    if(!oNewRs.IsBound())
      throw Exception("Could not create the Recordset object- MDAC may not 
be installed");

    oNewRs->CursorLocation = adUseClient;
    oNewRs->LockType       = adLockBatchOptimistic;
    oNewRs->CursorType     = adOpenStatic;

    OleVariant eParam;
    eParam.VType  = varError;
    eParam.VError = 0x80020004; //DISP_E_PARAMNOTFOUND

    TVariant v = (IUnknown*)iunk;

    OLECHECK(oNewRs->Open(v, eParam, -1, -1, -1));
    OLECHECK(oNewRs->QueryInterface(IID_IDispatch, (LPVOID*)oRs));
  }
  catch(Exception& e)
  {
     hResult = Error(e.Message.c_str(), IID_IRsXmlConvert, E_FAIL);
     if(*oRs != NULL)
       (*oRs)->Release();
     *oRs = NULL;
  }
  catch(...)
  {
     hResult = Error(_T("Catastrophic error: internal crash"), 
IID_IRsXmlConvert, E_UNEXPECTED);
     if(*oRs != NULL)
       (*oRs)->Release();
     *oRs = NULL;
  }

  return hResult;
}
//---------------------------------------------------------------------------

Mark

Re: TStreamAdapter, ADO.Recordset

#306

Author: Dmitry Konnov
Date: Mon, 10 Jul 2006 05:43

4 lines
981 bytes

Thank you, Mark

this may help.

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