It's desirable to have Hibernate log any warnings attached to a JDBC Connection, rather than hiding them from users. Further, under certain circumstances, some DBs (Sybase, especially) will attach warnings to every single Statement. This can cause eventual memory issues as the warnings build up in the cached Connections in the pool.

For now, log and clear when the Connection is released/closed. It would be better to do this at the Statement level, whenever one is executed, but that work would be substantial and pervasive. Once Steve Ebersole's JdbcSession work is finished, this may be easier to accomplish.