Hibernate的批量查询——Criteria查询所有、条件、分页、统计（聚合函数）、排序

1、查询所有的学生信息：

public static void testSel() {
            Session session = HibernateUtils.openSession();
            Transaction transaction = session.beginTransaction();
            Criteria criteria=session.createCriteria(Student.class);
            List<Student>list= criteria.list();
            System.out.println(list);
            transaction.commit();
            session.close();
        }

2、条件查询：

运算符与对应的英文缩写：

> gt　　>=ge　　<lt　　<=le　　==eq

!=ne　　in:in　　between and:：between

like:like　　is not null:isNotNull　　

or:or　　and:and

(1)eq的运用：

public static void testSel() {
            Session session = HibernateUtils.openSession();
            Transaction transaction = session.beginTransaction();
            Criteria criteria=session.createCriteria(Student.class);
            criteria.add(Restrictions.eq("sex","女"));
            List<Student>list= criteria.list();
            System.out.println(list);
            transaction.commit();
            sessio

（2）like的运用：

public static void testSel() {
            Session session = HibernateUtils.openSession();
            Transaction transaction = session.beginTransaction();
            Criteria criteria=session.createCriteria(Student.class);
            criteria.add(Restrictions.like("sname","许__"));
            List<Student>list= criteria.list();
            System.out.println(list);
            transaction.commit();
            session.close();
        }

3、分页查询：

需要事先设置起始位置和查询的数量。

public static void testSel() {
            Session session = HibernateUtils.openSession();
            Transaction transaction = session.beginTransaction();
            Criteria criteria=session.createCriteria(Student.class);
            criteria.add(Restrictions.eq("sex","女"));
            criteria.setFirstResult();
            criteria.setMaxResults();
            List<Student>list= criteria.list();
            System.out.println(list);
            transaction.commit();
            session.close();
        }

4、总记录数的获取：

 public static void testSel() {
            Session session = HibernateUtils.openSession();
            Transaction transaction = session.beginTransaction();
            Criteria criteria=session.createCriteria(Student.class);
            criteria.setProjection(Projections.rowCount());//聚合函数获得总行数
            Long rowNum= (Long) criteria.uniqueResult();
            System.out.println(rowNum);
            List<Student>list= criteria.list();
            System.out.println(list);
            transaction.commit();
            session.close();
        }

5、排序：

升序：

public static void testSel() {
        Session session = HibernateUtils.openSession();
        Transaction transaction = session.beginTransaction();
        Criteria criteria=session.createCriteria(Student.class);
        criteria.addOrder(Order.asc("studentno"));
        List<Student>list= criteria.list();
        System.out.println(list);
        transaction.commit();
        session.close();
    }

降序：

 public static void testSel() {
        Session session = HibernateUtils.openSession();
        Transaction transaction = session.beginTransaction();
        Criteria criteria=session.createCriteria(Student.class);
        criteria.addOrder(Order.desc("studentno"));
        List<Student>list= criteria.list();
        System.out.println(list);
        transaction.commit();
        session.close();
    }

5、Criteria 和 DetachedCriteria的区别

Criteria 和 DetachedCriteria 的主要区别在于创建的形式不一样， Criteria 是在线的，所以它是由 Hibernate Session 进行创建的；而 DetachedCriteria 是离线的，创建时无需Session。

例如下面的条件查询代码写在servlet中，没有与session进行连接：

 String cust_name = request.getParameter("cust_name");
        DetachedCriteria dc = DetachedCriteria.forClass(Customer.class);
        if(cust_name!=null && !"".equals(cust_name)){
            dc.add(Restrictions.like("cust_name", "%"+cust_name+"%"));
        }