We had this exception when moving from Hibernate 3.6.6 to 4.3.6. The newer version removes Hibernate.createBlob so we switched to session.getLobHelper.createBlob as suggested by the Javadoc. This caused the exception as per the description in this issue.

The fix for us was to use Hibernate.getLobCreator(session).createBlob since this creates the BLOB "contextually", i.e. it calls Connection.createBlob() to create the correct Oracle BLOB implementation class.