使用Criteria建立分组统计查询

//分组统计
ProjectionList projectionList = Projections.projectionList();
//group by  的属性值
projectionList.add(Projections.groupProperty("os"));
//统计行数
projectionList.add(Projections.rowCount());

Criteria c = factory.openSession().createCriteria(AdClick.class);
//设置查询条件		
c.setProjection(projectionList);