Hibernate之Query接口的uniqueResult()方法[通俗易懂]

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如果查询返回多个值用list()方法

1. public void testQuery(){
2. Configuration config = new Configuration().configure();
3. SessionFactory factory = config.buildSessionFactory(); //创建SessionFactory
4. Session session = factory.openSession(); //创建Session
5. session.beginTransaction(); //开始事务
7. Query query = session.createQuery(“from Student”);
8. List list = query.list(); // 用list方法返回多个值
9. //List list = session.createQuery(“from Student”).list();
10. for(int i=0;i<list.size();i++){
11. Student student = (Student)list.get(i);
12. System.out.print(student.getId()+” “);
13. System.out.print(student.getName()+” “);
14. System.out.print(student.getSex()+” “);
15. System.out.print(student.getBirthday());
16. System.out.println();
17. }
19. session.getTransaction().commit(); //提交事务
20. session.close(); //关闭Session
21. }

当确定返回的实例只有一个或者null时 用uniqueResult()方法

1. public void testGet(){
2. Configuration config = new Configuration().configure();
3. SessionFactory factory = config.buildSessionFactory();
4. Session session = factory.openSession();
5. session.beginTransaction();
7. Query query = session.createQuery(“from Student s where s.id=?”);
8. query.setString(0, “2”);
9. 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
10. //Student student = (Student)session.createQuery(“from Student s where s.id=?”).setString(0,”5″).uniqueResult();
12. System.out.println(student.getName());
13. System.out.println(student.getBirthday());
16. session.getTransaction().commit();
17. session.close();
18. }

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