Additional comment, I have tried holding the Connection as a private variable in the SLSB too only use one conneciton for the whole bean. I clean up only the ResultSet and Statement. I still get a ConnectionClosed error when the second method attempts to use the connection.
Just a question, not really an answer to your question:
since the connections are pooled AND cached, will you really feel a increase of performance with holding the connection in you bean instead of closing everything?