hibernte criteria只查询表的的某个字段:
Criteria criteria=session.createCriteria(User.class);
ProjectionList proList = Projections.projectionList();//设置投影集合
proList.add(Projections.groupProperty( "userName "));
proList.add(Projections.groupProperty( "password "));
criteria.setProjection(proList);
最后返回的List是 Object[] , [0] = userName, [1] = password