@Entity
@Table(name = "users")
@Getter
@Setter
public class User {

  @Id
  @Column(name = "user_id", nullable = false, updatable = false)
  private Long id;

  ...

}

@Repository
public interface UserRepository extends JpaRepository<User, Long> {

  @Override
  @PreAuthorize("#user.id == principal.username")
  void delete(User user);

  ...

}

java.lang.IllegalArgumentException: Failed to evaluate expression '#user.id == principal.username'
...
Caused by: org.springframework.expression.spel.SpelEvaluationException: EL1007E: Property or field 'id' cannot be found on null