Hi!
First of all. Thank you very much for such an useful tool like 
HibernateAppender.
We are logging our app's messages to Oracle.
But we met a problem when logs messages has a big size.

After view HibernateAppender source code, we've seen this error:
 Session session = null;
  try {
    session = hibernateSessionServiceImplementation.openSession();
// many code
//....................................................................
 session.flush();
 session.close();
 buffer.clear();
// many code
//....................................................................

 } catch (HibernateException he) {
     //And here WE ADDED THESE LINES TO AVOID PROGRAM CRASH   
//WHEN WE MEET A DATABASE ERROR
try{
       session.flush();
       session.close();
}catch(HibernateException ex){
       ex.printStackTrace();
}
            buffer.clear();
            appending = Boolean.FALSE;
            return;
}

We hope this correction could help you.
Thanks!