Eventually have found solution. Works for me.
public static void transactional2() {
com.avaje.ebean.Ebean.beginTransaction();
User user = User.query.getById(22l);
user.setPassword("qweqwe123");
user.save();
com.avaje.ebean.Ebean.rollbackTransaction();
// OR: com.avaje.ebean.Ebean.commitTransaction();
}
Please add you comments if something wrong with this solution.
Ebean documentation example: http://www.avaje.org/ebean/introtrans_begin.html