CODEWITHSUNDEEP
javajsonspring-bootpostman
wojciechw
wojciechw

Reputation: 81

JSON not showing how it should in Postman

I have some wierd behavior in my Postman when I try to invoke REST endpoints. There is a never-ending loop. I have found a solution on stackoverflow that @JsonIgnore annotation will remove this wierd loop (I have it in my Book entity below) but then when I try to list all books in Postman I do not see authors for those books. Is there a better solution to show books with authors (remove that @JsonIgnore annotation) but also remove that wierd loop?

Book.java

@Entity
public class Book {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String title;
    private String isbn;

    @ManyToMany
    @JsonIgnore // removed wierd loop with data
    @JoinTable(name = "author_book", joinColumns = @JoinColumn(name = "book_id"),
            inverseJoinColumns = @JoinColumn(name = "author_id"))
    private Set<Author> authors = new HashSet<>();

    public Book() {
    }

Author.java

@Entity
public class Author {

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

    @ManyToMany(mappedBy = "authors")
    private Set<Book> books = new HashSet<>();

    public Author() {
    }

BookController.java

@RestController
public class BookController {
    private BookService bookService;

    @Autowired
    public BookController(BookService bookService) {
        this.bookService = bookService;
    }

    // expose /books and get list of all books - GET
    @GetMapping("/api/books")
    public List<Book> getAllBooks() {
        return bookService.getAllBooks();
    }

AuthorController is the same as BookController.

This is how Book JSON looks in Postman (there are no authors for the books):

enter image description here

It's all ok with Authors in Postman:

enter image description here

And this is the loop when I remove @JsonIgnore from Book entity: enter image description here

Upvotes: 1

Views: 462

Answers (1)

Jonathan JOhx
Jonathan JOhx

Reputation: 5968

Use @JsonIgnoreProperties annotation in order to ignore the sub fields on a field, then this annotation will ignore the second level fields.

Book 
    - >  authors
                -> books  // this field is ignored

Author 
    - >  books
                -> authors // this field is ignored

@ManyToMany
@JsonIgnoreProperties("books")
@JoinTable(name = "author_book", joinColumns = @JoinColumn(name = "book_id"),
        inverseJoinColumns = @JoinColumn(name = "author_id"))
private Set<Author> authors = new HashSet<>();

@ManyToMany(mappedBy = "authors")
@JsonIgnoreProperties("authors")
private Set<Book> books = new HashSet<>();

Upvotes: 1

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