一对一映射 Hibernate

Posted 2023-02-24

【中文标题】一对一映射 Hibernate

【英文标题】：One to One mapping Hibernate

【发布时间】：2021-08-18 09:46:44

【问题描述】：

我有两个实体（用户、汽车）。有人可以告诉如何设置这个一对一的映射。我的代码不起作用。错误：org.hibernate.AnnotationException: Unknown mappedBy in: hiber.model.Car.user, referenced property unknown: hiber.model.User.car

用户实体包含加入到 mysql 列 carId 的 Car car 字段。此列是与 cars 表中的 id 链接的外键

@Entity
@Table(name = "users")
public class User 
    ...
    @OneToOne
    @JoinColumn(name = "carId")
    private Car car;
    ...

汽车实体包含用户用户字段

@Entity
@Table(name = "cars")
public class Car 
    ...
    @OneToOne(mappedBy = "car")
    private User user;
    ...


public class Main 
    ...
    UserService userService = context.getBean(UserService.class);
    CarService carService = context.getBean(CarService.class);
      
    User user1 = new User("User1", "Lastname1", "[e-mail]");
    Car car1 = new Car("Car", 1);
    
    carService.add(car1);
    user1.setCar(car1);
    userService.add(user1); 
    ...

@Service 和 @Repository 类：

public class UserServiceImpl 
    ...
    @Autowired
    private UserDao userDao;
   
    public void add(User user) 
      userDao.add(user);
    
    ...

在没有映射的情况下一切正常。实体分别写入数据库。

public class UserDaoImpl 
    ...
    @Autowired
    private SessionFactory sessionFactory;
    
    public void add(User user) 
      System.out.println(user.toString());
      sessionFactory.getCurrentSession().save(user);
    
    ...


public class CarServiceImpl 
    ...
    @Autowired
    private CarDao carDao;
    
    public void add(Car car) 
        carDao.add(car);
    
    ...


public class CarDaoImpl 
    ...
    @Autowired
    private SessionFactory sessionFactory;
    
    public void add(Car car) 
        sessionFactory.getCurrentSession().save(car);
    
    ...

【参考方案1】：

试试这个方法：

@Entity
@Table(name = "users")
public class User 
    ...
    @OneToOne
    @JoinColumn(name = "carId")
    private Car car;
    ...


@Entity
@Table(name = "cars")
public class Car 
    ...
    @OneToOne(mappedBy = "car")
    @JoinColumn(name = "userId")
    private User user;
    ...