Spring: Not-null property references a null or transient value

Question

I have an entity(Car) and i want to add records belong this entity with postman. My entity has one relational connection with User entity.

When i want to add a Car object to database, i get an error :

message=not-null property references a null or transient value : com.carnft.carr.entity.Car.user;

This is the entity that i want to add from postman:

@Entity
@Table(name = "car")
@Data
public class Car {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @JsonView(Views.Base.class)
    private String name;

    @JsonView(Views.Base.class)
    private String qtype;

    @JsonView(Views.Base.class)
    private int km;

    @JsonView(Views.Base.class)
    private String image;

    private boolean sellStatus=false;

    @ManyToOne(fetch = FetchType.LAZY,cascade = {CascadeType.ALL})
    @JoinColumn(name="user_id", nullable = false)
    @OnDelete(action = OnDeleteAction.CASCADE)
    @JsonIgnore
    User user;

}

And this is the method inside Car controller:

@PostMapping
public Car addCar(@RequestBody Car car){
    return carService.addCar(car);
}

And this is the service:

public Car addCar(Car car) {
        return carRepository.save(car);
    }

I neither add any car with postman or directly from mysql workbench.

Answer 1

Your attribute User user in Car entity has the annotation @JoinColumn(name="user_id", nullable = false) which force user to not be null.

When you save your Car entity, you must set a user entity to it with car.setUser(yourUserEntity). For now, your method addCar only save a car with carRepository.save(car);

Or you can remove nullable = false from your annotation.

Answer 2

I had the same problem long ago. You need to manually install lombok on your device or remove lombok and use getter and setter.