hibernate 查询无法排序

hql="from AskBuy as a where a.userID = ? order by ? desc ";Query query=session.createQuery(hql);query.setParameter(0, userId);                  query.setParameter(1,time);query.setMaxResults(5);

查询出来 排序无效. 纠结好久都没法解决，最后用拼字符串，改成

hql="from AskBuy as a where a.userID = ? order by time desc ";Query query=session.createQuery(hql);query.setParameter(0, userId);query.setMaxResults(5);

这样就可以，不知为何，待探索