I guess I was a little mistaken. I'm new at this forum, please forgive me if I'm wrong. In the first message I passed on the link and got to DuplicateKeyException javax.ejb.DuplicateKeyException. I thought that the developer decided not to create a DuplicateKeyException and instead use javax.ejb.DuplicateKeyException.
And as it turned out, the editor himself makes reference to the message.