FILE: OLE2BIN Sample - Storing COleClientItems in a Database

ID: Q177911

The information in this article applies to:

SUMMARY

The OLE2BIN sample demonstrates how to save and load an MFC COleClientItem from a Access database (.mdb file). The storage and any COleClientItem data are stored.

STEP2 of the Container tutorial sample was used as the starting point to demonstrate this technique. A Database menu was added, with two submenus, Save Object and Load Object. To save an object to the database, click a COleClientItem to select it and then click Save Object on the Database menu. You will be asked to provide a name for the object, which can then be used later to load the object from the database.

To load an object, click Load Object on the Database menu. You will be asked to select an object that was previously saved. When you first run the sample, there is an object that has already been placed in the database.


MORE INFORMATION

The following file is available for download from the Microsoft Software Library:

OLE2BIN.EXE
For more information about downloading files from the Microsoft Software Library, please see the following article in the Microsoft Knowledge Base:
Q119591 How to Obtain Microsoft Support Files from Online Services
The core functionality of the sample is located in two functions, CContainerView::OnDatabaseLoad() and CContainerView::OnDatabaseSave().

Below is the code for the OnDatabaseSave() function. The only item that is not well documented is the m_bForceFlat member. This member tells the archive to store the data without creating additional substorages. All the data is saved into the one stream.

NOTE: Because the COleClientItem is serialized, not only is the OLE storage saved, but all of the COleClientItem's data (position, display aspect, and so on) is also saved.

Here is the OnDatabaseSave() method:


   static const TCHAR szContents[] = _T("Contents");
   #define INITIAL_ALLOC_SIZE 100000

   void CContainerView::OnDatabaseSave()
   {
      LPLOCKBYTES pLockBytes = NULL;
      LPSTORAGE pStorage = NULL;

      ASSERT(m_pSelection != NULL);

      CNameDlg dlg;
      if (dlg.DoModal() == IDCANCEL || dlg.m_Name == "")
      {
         return;
      }

      CDatabase db;
      if (!db.OpenEx("DRIVER=Microsoft Access Driver
         (*.mdb);DBQ=BinDB.MDB;FIL=MS Access for Microsoft
         Access;UID=Admin;PWD=;"))
      {
         AfxMessageBox("Access ODBC Driver not installed");
         return;
      }

      CObjectSet rs(&db);
      rs.Open();
      rs.AddNew();

      rs.m_Name = dlg.m_Name;

      GlobalFree(rs.m_OleObject.m_hData);

      rs.m_OleObject.m_hData = GlobalAlloc(GMEM_MOVEABLE,
         INITIAL_ALLOC_SIZE);

      if (FAILED(CreateILockBytesOnHGlobal(rs.m_OleObject.m_hData,FALSE,
                   &pLockBytes)))
      {
         AfxMessageBox("Unable to retrieve LockBytes");
         return;
      }

      if (FAILED(StgCreateDocfileOnILockBytes(pLockBytes, STGM_DIRECT |
              STGM_CREATE | STGM_READWRITE | STGM_SHARE_EXCLUSIVE, 0,
              &pStorage)))
      {
        AfxMessageBox("Failure creating storage on LockBytes");
        pLockBytes->Release();
        return;
      }

      COleStreamFile file;
      CFileException fe;
      if (!file.CreateStream(pStorage, szContents,
            CFile::modeReadWrite|CFile::shareExclusive|CFile::modeCreate,
            &fe))
      {
        AfxThrowFileException(fe.m_cause, fe.m_lOsError);
      }

      // save to Contents stream
      CArchive saveArchive(&file, CArchive::store |
                             CArchive::bNoFlushOnDelete);
      saveArchive.m_pDocument = GetDocument();
      saveArchive.m_bForceFlat = TRUE;

      TRY
      {
          m_pSelection->Serialize(saveArchive);
          saveArchive.Close();
          file.Close();

          // commit the storage
          SCODE sc = pStorage->Commit(STGC_ONLYIFCURRENT);
          if (sc != S_OK)
            AfxThrowOleException(sc);
      }
      CATCH_ALL(e)
      {
          file.Abort();   // will not throw an exception
          THROW_LAST();
      }
      END_CATCH_ALL


      rs.SetFieldDirty(&rs.m_OleObject);
      rs.SetFieldNull(&rs.m_OleObject, FALSE);

      STATSTG statstg;
      pLockBytes->Stat(&statstg,  STATFLAG_NONAME);
      rs.m_OleObject.m_dwDataLength = statstg.cbSize.LowPart;

      rs.Update();
      rs.Close();

      pLockBytes->Release();
      pStorage->Release();
   }

Here is the OnDatabaseLoad() method, which is just the opposite of the OnDatabaseSave() method:


   void CContainerView::OnDatabaseLoad()
   {
      LPSTORAGE pStorage = NULL;
      LPLOCKBYTES pLockBytes = NULL;

      // Make certain there are objects in the database
      // If there are, bring up dialog for user to select an object
      CDatabase db;
      if (!db.OpenEx("DRIVER=Microsoft Access Driver
         (*.mdb);DBQ=BinDB.MDB;FIL=MS Access for Microsoft
         Access;UID=Admin;PWD=;"))
      {
         AfxMessageBox("Access ODBC Driver not installed");
         return;
      }

      CObjNameSet rsObjName(&db);

      rsObjName.Open();
      if (rsObjName.IsEOF())
      {
          rsObjName.Close();
          AfxMessageBox("No objects exist in the database.");
          return;
      }

      CObjDlg dlg(&rsObjName);
      if (dlg.DoModal() == IDCANCEL)
      {
         return;
      }

      rsObjName.Close();

      CObjectSet rs(&db);

      CContainerItem * pItem = new CContainerItem;

      rs.m_strFilter = "Name = '" + dlg.m_ObjectName + "'";

      rs.Open();

      if (FAILED(CreateILockBytesOnHGlobal(rs.m_OleObject.m_hData, FALSE,
                    &pLockBytes)))
      {
          AfxMessageBox("Unable to retrieve LockBytes");
          return;
      }

      HRESULT hr = StgOpenStorageOnILockBytes(pLockBytes, NULL,
                    STGM_DIRECT | STGM_READ | STGM_SHARE_EXCLUSIVE  , NULL,
                    0, &pStorage);

      if (FAILED(hr))
      {
         AfxMessageBox("Failure opening storage");
         pLockBytes->Release();
         return;
      }


      COleStreamFile file;
      CFileException fe;
      if (!file.OpenStream(pStorage, szContents,
             CFile::modeRead|CFile::shareExclusive, &fe))
      {
         if (fe.m_cause == CFileException::fileNotFound)
            AfxThrowArchiveException(CArchiveException::badSchema);
         else
            AfxThrowFileException(fe.m_cause, fe.m_lOsError);
      }

      CArchive loadArchive(&file, CArchive::load |
                           CArchive::bNoFlushOnDelete);
      loadArchive.m_pDocument = GetDocument();
      loadArchive.m_bForceFlat = TRUE;

      TRY
      {
         pItem->Serialize(loadArchive);     // load main contents
         loadArchive.Close();
         file.Close();
      }
      CATCH_ALL(e)
      {
         file.Abort();   // will not throw an exception
         // remove item because it didn't fully loaded
         GetDocument()->RemoveItem(pItem);
         THROW_LAST();
      }
      END_CATCH_ALL

      rs.Close();

      db.Close();

      pLockBytes->Release();

      GetDocument()->UpdateAllViews(NULL);
   }

Additional query words: OLE Field BLOB Binary kbVC500 kbVC600 


Keywords          : kbsample kbDatabase kbMFC kbODBC kbVC 
Version           : WINNT:5.0
Platform          : winnt 
Issue type        :

Last Reviewed: July 29, 1999