hibernate查询3

package one;import java.util.List;import org.hibernate.Criteria;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.cfg.Configuration;import org.hibernate.criterion.Projections;import org.hibernate.criterion.Restrictions;/*QBC 查询*/public class Demo3 { public static void main(String[] args) {Configuration config=new Configuration().configure();SessionFactory sf=config.buildSessionFactory();Session session=sf.openSession();Transaction trans=null;Criteria criteria = session.createCriteria(Students.class); criteria.add(Restrictions.gt("age", new Integer(20)));criteria.add(Restrictions.lt("age", new Integer(40))); criteria.setProjection(Projections.avg("age"));List studentsList = criteria.list();//studentsList.get double age=(Double)studentsList.get(0); System.out.println(age);//List listCrit=criteria.list();//Iterator iter=listCrit.iterator();//while(iter.hasNext()){//Students stu=(Students)iter.next();//System.out.print(stu.getName()+" " );//System.out.println(stu.getAge());//}////criteria.add(Restrictions.eq("name","rose"));//Students stu=(Students)criteria.uniqueResult();//System.out.println(stu.getName());//System.out.println(stu.getAge());}}/*Criteria criteria = session.createCriteria(Students.class);//按照学生姓名的升序进行排序criteria.addOrder(Order.asc("name"));//按照年龄的降序进行排序criteria.addOrder(Order.desc("age"));List studentsList = criteria.list(); */ /* * criteria.setFirstResult(9); criteria.setMaxResults(20); List studentsList = criteria.list(); * *//* * //设置最大结果集为1,即只返回一个对象criteria.setFirstResult(5);criteria.setMaxResults(1); Students students =(Students)criteria.uniqueResult(); * *//* * //设置最大结果集为1,即只返回一个对象criteria.setFirstResult(5);criteria.setMaxResults(1); Students students =(Students)criteria.uniqueResult();System.out.println(students.getName()); *//* * // 查询学生姓名为”rose”的所有Students持久对象criteria.add(Restrictions.eq("name", "rose"));List studentsList = criteria. list (); * *//* * // 查询年龄大于20且小于40的所有Students持久对象criteria.add(Restrictions.gt("age", new Integer(20)));criteria.add(Restrictions.lt("age", new Integer(40)));List studentsList = criteria. list (); * *//* * // 查询学生的平均年龄criteria.setProjection(Projections.avg("age"));List studentsList = criteria.list(); Double age=(Double)studentsList.get(0); System.out.println(age); * */////获得ProjectionList对象//ProjectionList projectionList = Projections.projectionList();//projectionList.add(Projections.groupProperty("age"));//projectionList.add(Projections.rowCount());////// 查询每个年龄各有多少个人//criteria.setProjection(projectionList);//List studentsList = criteria.list ();////Iterator iter=studentsList.iterator();//while(iter.hasNext()){////Students stuTemp=(Students)iter.next();////System.out.println(stuTemp.getAge());////Object []obj=(Object[])iter.next();//System.out.print(obj[0]+" ");//System.out.println(obj[1]);//}