Hibernate(4)Criteria查询（单表查询）

最新推荐文章于 2023-02-22 23:04:50 发布

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最新推荐文章于 2023-02-22 23:04:50 发布

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分类专栏： hibernate

本文链接：https://blog.youkuaiyun.com/qq_38125626/article/details/97642316

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本文详细介绍Hibernate Criteria API的各种查询方式，包括单表查询、条件查询、分页查询、查询总记录数、排序及离线查询对象。通过具体示例代码，展示如何使用Criteria进行高效的数据检索。

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Criteria 单表查询比较方便

Hibernate自创的无语局面向对象查询

查询所有对象

 /**
     * 查询所有对象
     */
    @Test
    public void test(){
        Session session = HibernateUtils.getCurrentSession();
        Transaction tx = session.beginTransaction();
        Criteria criteria = session.createCriteria(Customer.class);
        List<Customer> list = criteria.list();
        System.out.println(list);
        tx.commit();


    }

条件查询

 /**
     * 条件查询
     * >    gt
     * >=   ge
     * <    lt
     * <=   le
     * ==   eq
     * !=   ne
     * in   in
     * between and    between
     * like     like
     * is not null   isNotNull
     * is null       isNull
     * or        or
     * and   and
     */
    @Test
    public void test1(){
        Session session = HibernateUtils.getCurrentSession();
        Transaction tx = session.beginTransaction();

        //创建criteria查询对象
        Criteria criteria = session.createCriteria(Customer.class);
        //添加查询参数  查询cust_id id为1的custormer对象
        criteria.add(Restrictions.eq("cust_id",1));
        //List<Customer> list = criteria.list();
        Customer c = (Customer) criteria.uniqueResult();

        System.out.println(c);
        tx.commit();


    }

分页查询


    /**
     * 分页查询
     */
    @Test
    public void test2(){
        Session session = HibernateUtils.getCurrentSession();
        Transaction tx = session.beginTransaction();

        //创建criteria查询对象
        Criteria criteria = session.createCriteria(Customer.class);
        //limit ？，？  设置分页信息
        criteria.setFirstResult(1);
        criteria.setMaxResults(4);
        //执行查询
        List<Customer> list = criteria.list();
        //Customer c = (Customer) criteria.uniqueResult();

        System.out.println(list);
        tx.commit();


    }

查询总记录数、

 /**
     * 查询总记录数
     */
    @Test
    public void test3(){
        Session session = HibernateUtils.getCurrentSession();
        Transaction tx = session.beginTransaction();

        //创建criteria查询对象
        Criteria criteria = session.createCriteria(Customer.class);
        //设置查询的聚合函数
        criteria.setProjection(Projections.rowCount());
        //执行查询
        Long i = (Long) criteria.uniqueResult();
        //Customer c = (Customer) criteria.uniqueResult();

        System.out.println(i);
        tx.commit();


    }

排序

    /**
     * 排序
     */
    @Test
    public void test4(){
        Session session = HibernateUtils.getCurrentSession();
        Transaction tx = session.beginTransaction();

        //创建criteria查询对象
        Criteria criteria = session.createCriteria(Customer.class);
        //criteria.addOrder(Order.asc("cust_id"));
        criteria.addOrder(Order.desc("cust_id"));   //反向排序
        List<Customer> list = criteria.list();


        System.out.println(list);
        tx.commit();


    }

离线查询对象

@Test
public void test5(){
    //模拟web层或者service层   
    DetachedCriteria dc = DetachedCriteria.forClass(Customer.class);
    dc.add(Restrictions.idEq(6l));

    //~~~~~~~~~~~~~~~~~~~~dao层   可以不变对象多个查询条件  
    Session session = HibernateUtils.getCurrentSession();
    Transaction tx = session.beginTransaction();

    Criteria c = dc.getExecutableCriteria(session);
    List list = c.list();
    System.out.println(list);
    tx.commit();


}