CByteArrayFile - storing objects in databases using DAO

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You HongJiang contributed the CByteArrayFile class and article, and Daniel Kaminski contributed the demonstration application.

In my project I need to serialize some objects into a database field with DAO. However, I can not find any support for serializing anobject into database field. I had to implemented one by myself.

In this example, I will show you a class named CByteArrayFile. It is a derived class of CMemFile. With this class we can serialize objects into a CByteArray object. We can then use DFX_Binary to transfer data into a database "long binary" field.

Following is the sample code of how to use the CByteArrayFile class.

In the class which need to be serialized (such as CSomeClass):

CSomeClass::TransferDataWithByteArray(CByteArray& byteArray, BOOL bStore)
{
   CByteArrayFile byFile;
   byFile.SetArray(&byteArray);��� // attach byteArray with byFile

   
   if (bStore) // store object into byteArray

   {
      // create CArchive object with CByteArray File

      CArchive ar( &byFile, CArchive::store);
 
      // Call CSomeClass::Serialize function

      Serialize(ar);

      ar.Close();
   }
   else // load object from byteArray

   {
     CArchive ar( &byFile, CArchive::load);
     Serialize(ar);��� // Call CSomeClass::Serialize function

     ar.Close();
   }
 
  // important!! detach byteArray with byFile. Or byteArray will be 

  // free with byFile

  byFile.Detach();
}

CSomeDaoRecordset rs;��� // rs.m_byteLongField is a CByteArray class

CSomeClass object;

// 1. Write to record

rs.Open(. . .);
rs.AddNew();
object.TransferDataWithByteArray(rs.m_byteLongField, TRUE /* store */);
. . .
rs.Update();
rs.Close();

// 2. Read from record

rs.Open(. . .);
object.TransferDataWithByteArray(rs.m_byteLongField, FALSE /* load */);
...

rs.Close();