Return IDs in JSON response from Spring Data REST

I've got an entity

@Entity
@Table(name = "books")
public class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String name;

    @Column(name = "id", unique = true, nullable = false)
    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    @Column(name = "name")
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

I initialize it like this

@PostConstruct
public void init() {
    List<String> newFiles = this.listFiles();
    newFiles.forEach(filename -> {
        Book book = new Book();
        book.setName(filename);

        dbRepository.save(book);
    });
}

If I set the result of save to an instance of Book, I can get the id and it is not null—so id is created fine.

I defined a repository

@RepositoryRestResource
public interface IBooksRepository extends CrudRepository<Book, Long> {
}

which I'd like to use to get and set data into the books table in the database.

When I try to access my repository rest using curl localhost:8080/books, I get this response

{
   "_embedded":{
      "books":[
         {
            "name":"simple-file.txt",
            "_links":{
               "self":{
                  "href":"http://localhost:8080/books/1"
               },
               "book":{
                  "href":"http://localhost:8080/books/1"
               }
            }
         }
      ]
   },
   "_links":{
      "self":{
         "href":"http://localhost:8080/books"
      },
      "profile":{
         "href":"http://localhost:8080/profile/books"
      }
   }
}

The books element returns name only. How can I make it return id too, on the same level as name?

Solution

Spring Data Rest hides the ID by default, in order to have it in the JSON you have to manually configure that for your entity. Depending on your spring version you can either provide your own configuration (old):

@Configuration
public class ExposeEntityIdRestConfiguration extends RepositoryRestMvcConfiguration {

    @Override
    protected void configureRepositoryRestConfiguration(RepositoryRestConfiguration config) {
        config.exposeIdsFor(Book.class);
    }
}

...or register a RepositoryRestConfigurer (current):

@Component
public class ExposeEntityIdRestMvcConfiguration extends RepositoryRestConfigurerAdapter {

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

See the Spring Data Rest documentation for more details.