hibernate中查询一个对象时使用悲观锁

session = sessionFactory.openSession();
tx = session.beginTransaction();
Query q = session.createQuery("from SequenceTable se where se.key = ?");
q.setString(0, key);
q.setLockMode("se", LockMode.UPGRADE);
List list = q.list();
if (list == null || list.size() == 0){
 tx.rollback();
}
Sequence seq = (Sequence)list.get(0);
session.update(seq);
tx.commit();