父实体的主键未在子实体中存储为外键

Question

I am using OneToMany relationship in spring data Jpa and testing the api using postMan

@Entity
@Table(name = "book_category")
public class BookCategory {
ParentEntity
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "bookCat_id")
    private Long id;

    private String name;

    @OneToMany(cascade = CascadeType.ALL, mappedBy="bookCategory")
    private Set<Book> books;

    public BookCategory(String name, Set<Book> books) {
        this.name = name;
        this.books = books;
    }

// getter and setter

}

ChildEntity


    @Entity
    @Table(name = "book")
    public class Book {

        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        @Column(name = "book_id")
        private Long bookId;

        private String name;

        @ManyToOne(cascade = CascadeType.PERSIST)
        @JoinColumn(name = "bookCat_id")
        BookCategory bookCategory;

        public Book() {

        }

    //getter  and Setter

    }

ControllerClass

@RestController
@RequestMapping(value = "/bookCategory")
public class BookController {

    @Autowired
    BookCategoryRepository bookCategoryRepository;

    @Autowired
    BookRepository bookRepository;

    @PostMapping("/addBookCategory")
    public BookCategory savePerson(@Valid @RequestBody BookCategory bookCategory){
        return bookCategoryRepository.save(bookCategory);
    }
}

calling Rest Api from postman and passing json as

{

    "name":"Category 1",
    "books":[
          {"name" : "Hello Koding 1"},
          {"name":"Hello Koding 2"}
        ]
} 

Following Query is executing by hibernate query is also correct while i am calling rest point the thing Hibernate: insert into book_category (name) values (?) Hibernate: insert into book (book_cat_id, name) values (?, ?)

it is not inserting book_cat_id, in book_cat_id it is passing null so null is getting store

Data stored in database book_category Parent Table in database

book(ChildTable) book(ChildTable) I want to get Child Table Like I want my table like this

Answer 1

The problem is that you are not setting parent in child object. Somewhere in the code you should call the

public void setBookCategory(BookCategory bookCategory) { ... }

method of the Book entity.

I'd suggest to resolve this issue by using DTOs in controller and mapping them to entities in service layer, as using peristent entities as parameters of http requests can lead to serious security vulnerabilities as explained here .

EDIT: Alternatively, even thought I would not encourage this solution would be to modify the savePerson method like this

@PostMapping("/addBookCategory")
public BookCategory savePerson(@Valid @RequestBody BookCategory bookCategory){
    bookCategory.getBooks().forEach(book -> book.setBookCategory(bookCategory));
    return bookCategoryRepository.save(bookCategory);
}