Hibernate的hql语句多种返回结果示例

ゝ一纸荒年。 2022-04-13 06:19 215阅读 0赞

### 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();
        }