Hibernate HQL

Posted 2021-03-10 Kikyo

HibernateHQL

public class HibernateHQL {
    //演示聚集函数使用
    @Test
    public void testSelect7() {
        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction tx = null;
        try {
            sessionFactory = HibernateUtils.getSessionFactory();
            session = sessionFactory.openSession();
            tx = session.beginTransaction();

            //1 创建query对象
            Query query = session.createQuery("select count(*) from Customer");

            //2 调用方法得到结果
            //query对象里面有方法，直接返回对象形式
            Object obj = query.uniqueResult();

            //返回int类型
//            int count = (int) obj;

            //首先把object变成long类型，再变成int类型
            Long lobj = (Long) obj;
            int count = lobj.intValue();
            System.out.println(count);

            tx.commit();
        } catch (Exception e) {
            e.printStackTrace();
            tx.rollback();
        } finally {
            session.close();
            sessionFactory.close();
        }
    }

    //演示投影查询
    @Test
    public void testSelect6() {
        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction tx = null;
        try {
            sessionFactory = HibernateUtils.getSessionFactory();
            session = sessionFactory.openSession();
            tx = session.beginTransaction();

            //1 创建query对象
            Query query = session.createQuery("select custName from Customer");

            //2 调用方法得到结果
            List<Object> list = query.list();

            for (Object object : list) {
                System.out.println(object);
            }

            tx.commit();
        } catch (Exception e) {
            tx.rollback();
        } finally {
            session.close();
            sessionFactory.close();
        }
    }

    //演示分页查询
    @Test
    public void testSelect5() {
        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction tx = null;
        try {
            sessionFactory = HibernateUtils.getSessionFactory();
            session = sessionFactory.openSession();
            tx = session.beginTransaction();

            //1 创建query对象
            //写查询所有的语句
            Query query = session.createQuery("from Customer");

            //2 设置分页数据
            //2.1 设置开始位置
            query.setFirstResult(0);
            //2.2 设置每页记录数
            query.setMaxResults(3);

            //3 调用方法得到结果
            List<Customer> list = query.list();

            for (Customer customer : list) {
                System.out.println(customer.getCid() + "::" + customer.getCustName());
            }

            tx.commit();
        } catch (Exception e) {
            tx.rollback();
        } finally {
            session.close();
            sessionFactory.close();
        }
    }

    //演示排序查询
    @Test
    public void testSelect4() {
        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction tx = null;
        try {
            sessionFactory = HibernateUtils.getSessionFactory();
            session = sessionFactory.openSession();
            tx = session.beginTransaction();

            //1 创建query对象
            Query query = session.createQuery("from Customer order by cid desc");

            //2 调用方法得到结果
            List<Customer> list = query.list();

            for (Customer customer : list) {
                System.out.println(customer.getCid() + "::" + customer.getCustName());
            }

            tx.commit();
        } catch (Exception e) {
            tx.rollback();
        } finally {
            session.close();
            sessionFactory.close();
        }
    }

    //演示条件查询-模糊查询
    @Test
    public void testSelect3() {
        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction tx = null;
        try {
            sessionFactory = HibernateUtils.getSessionFactory();
            session = sessionFactory.openSession();
            tx = session.beginTransaction();

            //1 创建query对象
            Query query = session.createQuery("from Customer c where c.custName like ?");

            //2 设置？的值
            // %浪%
            query.setParameter(0, "%度%");

            //3 调用方法得到结果
            List<Customer> list = query.list();

            for (Customer customer : list) {
                System.out.println(customer.getCid() + "::" + customer.getCustName());
            }

            tx.commit();
        } catch (Exception e) {
            tx.rollback();
        } finally {
            session.close();
            sessionFactory.close();
        }
    }

    //演示条件查询
    @Test
    public void testSelect2() {
        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction tx = null;
        try {
            sessionFactory = HibernateUtils.getSessionFactory();
            session = sessionFactory.openSession();
            tx = session.beginTransaction();

            //1 创建query对象
            //SELECT * FROM t_customer WHERE cid=? AND custName=?
            Query query = session.createQuery("from Customer c where c.cid=? and c.custName=?");

            //2 设置条件值
            // 向？里面设置值
            // setParameter方法两个参数
            // 第一个参数：int类型是？位置，？位置从0开始
            // 第二个参数：具体参数值
            //设置第一个？值
            query.setParameter(0, 5);
            //设置第二个？值
            query.setParameter(1, "百度");

            //3 调用方法得到结果
            List<Customer> list = query.list();

            for (Customer customer : list) {
                System.out.println(customer.getCid() + "::" + customer.getCustName());
            }

            tx.commit();
        } catch (Exception e) {
            tx.rollback();
        } finally {
            session.close();
            sessionFactory.close();
        }
    }

    //演示查询所有
    @Test
    public void testSelect1() {
        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction tx = null;
        try {
            sessionFactory = HibernateUtils.getSessionFactory();
            session = sessionFactory.openSession();
            tx = session.beginTransaction();

            //1 创建query对象
            Query query = session.createQuery("from Customer");
            //2 调用方法得到结果
            List<Customer> list = query.list();

            for (Customer customer : list) {
                System.out.println(customer.getCid() + "::" + customer.getCustName());
            }

            tx.commit();
        } catch (Exception e) {
            tx.rollback();
        } finally {
            session.close();
            sessionFactory.close();
        }
    }
}