hibernate 查詢無法排序

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);

查詢出來 排序無效. 糾結好久都沒法解決，最後用拼字符串，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);

這樣就可以，不知爲何，待探索