I don't fully know the answer, but here are a couple thoughts.
I highly doubt you need to explore JDBC. If ODBC works for fetching info, it should work for everything.
I speculate that the problem is that you are trying to insert a variable of type int16 into a field that is defined as uint8. Just as an experiment, I would try updating the database field with exactly the same field that you just selected from it. That way you could eliminate some uncertainty from the update.