How to always return entity @Id when using JpaRepository?

Question

Having a @ReposirotyRestResource bound to an entity AppUser and extending the JpaRepository like this:

@RepositoryRestResource(collectionResourceRel = "users", path = "users")
public interface AppUserRepository extends JpaRepository<AppUser, Long> {

    AppUser findByUsername(@Param("username") String username);

}

Where AppUser looks like this:

@Entity
@Table(name = "app_user")
public class AppUser extends AbstractTimestampEntity {

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

    // ..
}

I want to receive the id whenever I want to appUserRepository.findUserByUsername("whatever") - for some reason the default behavior seems to be to not return this field.

---

Extra points for either pointing out an error on my side or explain to me why this is the default behavior (and a good idea).

Answer 1

Your question is about Spring Data REST (you should update tags) - it automatically 'transforms' your repositories to REST controllers with HATEOES where resource ID is the part of included to the resource self link, like: /appUsers/1. So by default resource body does not contain its ID.

If you need to include it you can extend RepositoryRestConfigurerAdapter and add exposing ID of necessary classes, for example like the follow:

@Bean
public RepositoryRestConfigurerAdapter repositoryRestConfigurerAdapter() {
    return new RepositoryRestConfigurerAdapter() {

        @Override
        public void configureRepositoryRestConfiguration(RepositoryRestConfiguration config) {
            config.exposeIdsFor(AppUser.class);
            super.configureRepositoryRestConfiguration(config);
        }
    };
}