在 Spring Boot REST API 中发送 json 中的外键时出错？

Question

我正在制作一个简单的应用程序。它有两个实体，即书本和地址。书有作者实例，因为它们具有一对一的关系。如果我将作者实例与书籍一起发送，它工作正常，但是当我发送已经存在的作者 ID 时，我会收到持久对象异常。请帮帮我。

@Table(name = "books")
public class Book {

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

    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "author_id",referencedColumnName = "id")
    private Author author;

    public Book(Long id,String title,Author author) {
        this.id = id;
        this.title = title;
        this.author = author;
    }}

@Entity
@Table(name = "authors")
public class Author {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String firstName;
    private String lastName;

    public Author(Long id, String firstName, String lastName) {
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
    }}


@Service
public class BookService {

    @Autowired
    private BookRepository repository;

    public List<Book> find() {
        return repository.findAll();
    }

    public Book find(Long id) {
        return repository.findById(id).get();
    }

    public Book save(Book book) {
        return repository.save(book);
    }
}

@RestController
@RequestMapping("/books")
public class BookController {

    @Autowired
    private BookService bookService;

    @GetMapping
    public List<Book> find(){
        return bookService.find();
    }

    @GetMapping(path = "{id}")
    public Book find(@PathVariable Long id){
        return bookService.find(id);
    }

    @PostMapping
    public Book find(@RequestBody Book book){
        return bookService.save(book);
    }
}

我正在发送的 Json 响应：

{ "title" : "你好 Java", “作者” ： { “身份证”：1 } }

Answer 1

在 JSON 响应中给出完整的作者对象，而不是只给出他的 id，

{ "title" : "Hello Java", "author" : { "firstName": "something", "lastName":"something"} }

这样做，不要提供作者 ID，然后将创建具有所需作者姓名的对象。