Question

我得到一个反序列化为POJO的JSON，我试图使用modelmapper将POJO映射到下面的实体类，并尝试将这些实体保存到数据库中。所有字段都按预期方式映射和保存，除了外键值为空。另外，该用户ID是自动生成的。请问我如何使用modelmapper将用户ID保存在车辆表中？

我的User实体类

@Entity
@Table(name = "usr")
class User{
    @Id
    @Column(name = "user_id", updatable = false, nullable = false)
    @GeneratedValue(strategy = GenerationType.IDENTITY)
        private Long userId;
        private String username;
        @OneToMany(mappedBy = "user",cascade = CascadeType.ALL)
        private List<Vehicle> vehicles= new ArrayList<>();
        //getters and setters
}

我的Vehicles实体类：

@Entity
@Table(name = "vehicle")
class Vehicle{
    @Id
    @Column(name = "vehicle_id", updatable = false, nullable = false)
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long vehicleId;
    private String vehicleName;
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "user_fk" , nullable = false)
    private User user;
    //getters and setters 
}

我的ModelMapping类：

@Service
public class UserService {

    @Autowired
    private UserDetailsService userDetailsService;

    public void saveUserDetails(UserDetails userDetails
        User targetuser{
            UserDetails sourcePojo= userDetails
            User  targetEntity= targetuser
            ModelMapper modelMapper = new ModelMapper();
            modelMapper.map(sourcePojo, targetEntity);

            userDetailsService.save(targetEntity);
    }
}

Answer 1

您可以尝试使注释更具体：

    @OneToMany(mappedBy = "user", 
               targetEntity = Vehicle.class,
               cascade = CascadeType.ALL)
    private List<Vehicle> vehicles= new ArrayList<>();

和

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "user_fk" , 
                referencedColumnName = "user_id",
                nullable = false)
    private User user;

我认为您必须删除注释才能自动生成用户ID 根据我的理解，问题是由于在将条目保存到DB时自动生成了userid。但是，当我们将用户ID映射到车辆时，它是null，因为它不会生成。

使用模型映射器的外键映射

1 个答案: