[FIXED] @OneToOne or @ManyToOne on package.BookingEntity.roomId references an unknown entity: long

Issue

I am trying to create a OneToOne relationship between two entities but I get this error:

@OneToOne or @ManyToOne on backendservice.entity.BookingEntity.roomId references an unknown entity: long

My entities

@Data
@Entity(name = "bookings")
public class BookingEntity {

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

  @OneToOne(cascade = CascadeType.ALL)
  @JoinColumn(name = "fk_roomId", referencedColumnName = "id")
  private Long roomId;

  @Column(name = "booked_by")
  private String bookedBy;

  @Column(name = "date_booked")
  private String dateBooked;
}

---

@Data
@Entity(name = "rooms")
public class RoomEntity {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  @Column(name = "id")
  private Long id;

  @Column(name = "room_name")
  private String roomName;

  @OneToOne(mappedBy = "fk_roomId")
  private BookingEntity bookingEntity;
}

---

Solution

In the association field you should use an actual entity, not just Long field. So this code:

@OneToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "fk_roomId", referencedColumnName = "id")
private Long roomId;

should be changed on something like

@OneToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "fk_roomId", referencedColumnName = "id")
private RoomEntity room;

Additionally I would like to note that for performance considerations it is highly recommended to declare your associations as lazy:

@OneToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)

Answered By - Eugene