Hibernate: How to display data from multiple table

Question

I am new in spring/hibernate technologies, I have tried to find an information about it, but failed, so if you can help I will be so thankful!

I need to display a JSON response in browser of multiple tables, one of the table has primary key for another one.

My entities:

@Entity
@Table
@ToString
public class Book {
    @Id
    @GeneratedValue(strategy = AUTO)
    @JsonView(Views.IdName.class)
    private Long book_id;

    @JsonView(Views.IdName.class)
    private String name;

    @Column(length = 1000000)
    private String text;


    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name="author_id")
    @JsonView(Views.IdName.class)
    private Author author;

    // ....get/set methods

Another one:

@Entity
@Table
@ToString
public class Page {
    @Id
    @GeneratedValue(strategy = AUTO)
    private Long id;

    @Column(length = 1000000)
    private String text;

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "book_id")
    private Book book;

    // ...get/set methods

My controllers:

@RestController
@RequestMapping("books")
public class BookController {
    private final BookRepo bookRepo;

    @Autowired
    public BookController(BookRepo bookRepo) {
        this.bookRepo = bookRepo;
    }

    @GetMapping
    @JsonView(Views.IdName.class)
    public List<Book> getAll() {
        return bookRepo.findAll();
    }

    @GetMapping("{id}")
    public Book getOne(@PathVariable("id") Book book) {
        return book;
    }
}

Another one:

@RestController
@RequestMapping("authors")
public class AuthorController {
    private final AuthorRepo authorRepo;

    @Autowired
    public AuthorController(AuthorRepo authorRepo) {
        this.authorRepo = authorRepo;
    }

    @GetMapping
    public List<Author> getAll() {
        return authorRepo.findAll();
    }

    @GetMapping("{id}")
    public Optional<Author> getOne(@PathVariable("id") Long id) {
        return authorRepo.findById(id);
    }
}

And also repo for interaction with DB (they are the similar):

public interface AuthorRepo extends JpaRepository<Author, Long> {
}

So when I make a request for get all books, I take the following JSON:

enter image description here

Bit I want different result, something like:

[
    {
        "book_id" : 1,
        "name": "name 1 book",
        "author" : 
                  {
                      "author_id" : 1,
                      "name": "some_name"
                  } 
    }
]

Also, when I tried to make a request for /authors/1, I will get the following response (something like recursion) :

enter image description here

So any help how can I handle with it? Thank you!

Answer 1

You can use a @NoRepositoryBean

like in this example:

@NoRepositoryBean
public interface MappedTypeRepository<T extends AbstractMappedType>
  extends Repository<T, Long> {

  @Query("select new com.example.YourObjectWithConstructor(e.attribute, sub.sub_attribute) from entity e inner join e.subtable sub where e.attribute = ?1")
  List<YourObjectWithConstructor> findAllByAttribute(String attribute);
}

My example may not be 100% correct, I did not check the syntax. Feel free to explore it
Check this also: JPQL Create new Object In Select Statement - avoid or embrace?