java - Spring boot REST api，在外键上传递 id 而不是整个对象

Question

我正在尝试使用 Spring boot 应用程序为 Web 和移动应用程序构建 REST API。在我的应用程序中，我有多个外键，并且我只想传递对象的 id 而不是整个对象。请参阅下面的示例。

模型书

// imports

@Entity
public class Book {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    private String title;
    private String isbn;

    @ManyToOne
    @JoinColumn(name = "category_id", updatable = false)
    private BookCategory bookCategory;

    public Book() {
    }

    public Book(Integer id, String title, String isbn, BookCategory bookCategory) {
        this.id = id;
        this.title = title;
        this.isbn = isbn;
        this.bookCategory = bookCategory;
    }

    // getters and setters
}

型号类别

// imports

@Entity
public class BookCategory {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    private String name;

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

    public BookCategory() {
    }

    public BookCategory(Integer id, String name) {
        this.id = id;
        this.name = name;
    }

    // getters and setters
}

图书 Controller

// imports

@RestController
@RequestMapping(path = "/api/v1")
public class BookController {

    @Autowired
    private BookRepository bookRepository;

    // other methods for index, show, put and delete

    @PostMapping(path = "/books")
    public book createBook(@RequestBody Book book) {
        return bookRepository.save(book);
    }

}

图书存储库

// imports

public interface BookRepository extends PagingAndSortingRepository<Book, Integer> {
}

书籍类别已预先加载到数据库中，我不想允许客户更改它们或添加新类别。

这是我尝试过的 JSON POST 以及存储在数据库中的对象。

请求

{
    "title": "Tirant lo blanc",
    "isbn": "9788475841199",
    "category_id": 4
}

回应

{
    "title": "Tirant lo blanc",
    "isbn": "9788475841199",
    "bookCategory": null
}

我也尝试将其作为对象发送，但结果为空。

{
    "title": "Tirant lo blanc",
    "isbn": "9788475841199",
    "category_id": {
        "id": 4
    }
}

如何发送类别 ID 以将书籍正确存储在数据库中？发送整个类别对象是否更好？我也尝试过，但是响应和数据库中存储的书籍始终处于类别 null。

Answer 1

如果您只想传递对象的 id，请设置您希望其返回的 getters。

例如:

// imports

@Entity
public class Book {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    private String title;
    private String isbn;

    @ManyToOne
    @JoinColumn(name = "category_id", updatable = false)
    private BookCategory bookCategory;

    public Book() {
    }

    public Book(Integer id, String title, String isbn, BookCategory bookCategory) {
        this.id = id;
        this.title = title;
        this.isbn = isbn;
        this.bookCategory = bookCategory;
    }

   // getters
   public Integer getBookCategory() {
        return bookCategory.getId();
   }
}