Hibernate的hql语句多种返回结果示例

返回单个对象

public static void test1(){
   Session session = SessionFactoryUtils.openSession();
   Transaction transaction = session.beginTransaction();
        String hql="from Student where sid=1";
        Query query = session.createQuery(hql);
        Object obj = query.getSingleResult();
        System.out.println(obj.getClass().getName());
        System.out.println(obj);
        transaction.commit();
        SessionFactoryUtils.closeSession();
    }

返回多个对象

/**
     * hql语句结果集处理情况1
     * 返回多个对象  注意数据库字段不能为null
     */
    public static void test2(){
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        String hql="from Student";
        Query query = session.createQuery(hql);
        List list=query.list();
        for (Object o : list) {
            System.out.println(o);
        }
        transaction.commit();
        SessionFactoryUtils.closeSession();
    }

返回字符串

public static void test3(){
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        String hql="select sname from Student where sid=1";
        Query query = session.createQuery(hql);
        Object obj=query.getSingleResult();
        System.out.println(obj);
        transaction.commit();
        SessionFactoryUtils.closeSession();
    }

返回数组

public static void test4(){
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        String hql="select sid,sname,version from Student where sid=1";
        Query query = session.createQuery(hql);
        Object obj=query.getSingleResult();
        System.out.println(Arrays.toString((Object[])obj));
        transaction.commit();
        SessionFactoryUtils.closeSession();
    }

返回Map

public static void test5(){
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        String hql="select new map(sid as sid,sname as sname,version as version) from Student where sid=1";
        Query query = session.createQuery(hql);
        Object obj=query.getSingleResult();
        System.out.println(obj);
        transaction.commit();
        SessionFactoryUtils.closeSession();
    }

查询多列返回对象（对象需要有有参和无参的构造函数）

public static void test6(){
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        String hql="select new Student (sid,sname)from Student where sid=1";
        Query query = session.createQuery(hql);
        Object obj=query.getSingleResult();
        System.out.println(obj.getClass().getName());
        System.out.println(obj);
        transaction.commit();
        SessionFactoryUtils.closeSession();
    }

:命名参数

public static void test7(){
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        String hql="from Student where sid in :ids";
        Query query = session.createQuery(hql);
        //这里使用 query.setParameter(0,1)报错
      // query.setParameter("id",1);//这个是传单个参数
        // 如果使用in的话
        List ids=new ArrayList();
        ids.add(1);
        ids.add(2);
        query.setParameterList("ids",ids);
        Object obj = query.getSingleResult();
        System.out.println(obj.getClass().getName());
        System.out.println(obj);
        transaction.commit();
        SessionFactoryUtils.closeSession();
    }

连表查询

public static void test8(){
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
       String hql="select new map(oi.order_item_id,o.order_id)  from  Order o,OrderItem oi where o.order_id=oi.oid ";
        Query query = session.createQuery(hql);
        List list=query.list();
        for (Object o : list) {
            System.out.println(o);
        }
        transaction.commit();
        SessionFactoryUtils.closeSession();
    }

聚合函数   其余的sum,avg,min,max用法都一样

public static  void test9(){
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        String hql="select count(sid)from Student ";
        Query query = session.createQuery(hql);
        Object singleResult = query.getSingleResult();
        System.out.println(singleResult);
        transaction.commit();
        SessionFactoryUtils.closeSession();
    }

hql分页

public static void test10() {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        String hql = "from Book ";
        Query query = session.createQuery(hql);
        int page = 2;
        int offeset = 3;
        query.setFirstResult(page * offeset);
        query.setMaxResults((page - 1) * offeset);
        List list = query.list();
        for (Object o : list) {
            System.out.println(o);
        }
        transaction.commit();
        SessionFactoryUtils.closeSession();
    }