问为什么deleteById采用双向方法？

EN

@Entity
@Table(name = "chilling_unit")
@Data
@NoArgsConstructor
public class ChillingUnitMonitoringDetailsDAO<T> {

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

  @Column(name="edge_controller_serial_number",nullable = false)
  private String l3SerialNumber;

  @Column(name = "product_type_name")
  private String productType;

  @ManyToOne(fetch = FetchType.EAGER, optional = false,cascade = javax.persistence.CascadeType.ALL
  @JoinColumn(name = "location_id")
  @OnDelete(action = OnDeleteAction.CASCADE)
  @JsonIgnore
  @EqualsAndHashCode.Exclude
  private LocationDAO location;

}

@Entity
@Table(name = "location")
@Data
@NoArgsConstructor
public class LocationDAO {

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

  @Column(name = "location_id",unique = true)
  private String locId;

}

public interface ChillingUnitMonitoringRepository<T> extends JpaRepository<ChillingUnitMonitoringDetailsDAO<T>,Long> {

}