If JDBC is not an option, you're left with native drivers in which case we're most probably talking about ODBC. Again, if JDBC-ODBC bridge isn't an option, the only way is to use the native driver is through JNI.
there is SQLJ but that compiles into jdbc anyway. There is of course plenty of other solutions that act as a layer between your app & jdbc (JDO, CMP for example). maybe explain why you don't want to use jdbc?