Hibernate之Query接口的uniqueResult()方法

如果查询返回多个值用list()方法

public void testQuery(){
        Configuration config = new Configuration().configure();
        SessionFactory factory = config.buildSessionFactory(); //创建SessionFactory
        Session session = factory.openSession();        //创建Session
        session.beginTransaction();                     //开始事务

        Query query = session.createQuery("from Student");
        List list = query.list();  // 用list方法返回多个值
        //List list = session.createQuery("from Student").list();
        for(int i=0;i<list.size();i++){
            Student student = (Student)list.get(i);
            System.out.print(student.getId()+" ");
            System.out.print(student.getName()+" ");
            System.out.print(student.getSex()+" ");
            System.out.print(student.getBirthday());
            System.out.println();
        }

        session.getTransaction().commit();         //提交事务
        session.close();                           //关闭Session
    }

当确定返回的实例只有一个或者null时 用uniqueResult()方法

public void testGet(){
        Configuration config = new Configuration().configure();
        SessionFactory factory = config.buildSessionFactory();
        Session session = factory.openSession();
        session.beginTransaction();

        Query query = session.createQuery("from Student s where s.id=?");
        query.setString(0, "2");
        Student student = (Student)query.uniqueResult();  //当确定返回的实例只有一个或者null时 用uniqueResult()方法
        //Student student = (Student)session.createQuery("from Student s where s.id=?").setString(0,"5").uniqueResult();

        System.out.println(student.getName());
        System.out.println(student.getBirthday());


        session.getTransaction().commit();
        session.close();
    }