java - 在 postman 中发送有效负载时，有没有办法从另一个表的主键插入外键值的值？

Question

Author.java:

package com.abc.entity;    

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

    @Id
    @Column(nullable=false, name="id")
    @SequenceGenerator(sequenceName="author_seq", name="a_seq")
    @GeneratedValue(generator="a_seq", strategy=GenerationType.SEQUENCE)
    private Integer id;

    @Column(nullable=false, name="first_name")
    @NotBlank(message = "First Name is required")
    private String firstName;

    @Column(name="last_name")
    @NotNull(message = "Last Name is required")
    private String lastName;

    @Column(name = "email", unique = true)
    @NotNull(message="email cannot be null")
    @Email
    @Pattern(regexp="[A-Za-z0-9._%-+]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}")
    private String email;

    @NotNull(message="Password")
    @Size(min=8, max=16, message="Password must be >= 8 and <=16 ")
    private String password;

    @OneToMany(/*orphanRemoval = true,*/
            //mappedBy="author",
            cascade=CascadeType.ALL) 
    private List<Book> books = new ArrayList<Book>();



    /**
     * Adding a book and in turn setting it author to this object
     * @param book
     */
    public void addBook(Book book) {
        books.add(book);
        book.setAuthor(this);
    }

    /**
     * Removing a book from the author
     * @param book
     */
    public void removeBook(Book book) {
        books.remove(book);
        book.setAuthor(null);
    }
}

Book.java:

package com.abc.entity;

@Data
@Entity
@Table(name="book")
public class Book {
    @Id
    @Column(nullable=false, name="id")
    @SequenceGenerator(sequenceName="book_seq", name="b_seq")
    @GeneratedValue(generator="b_seq", strategy=GenerationType.SEQUENCE)
    private Long id;

    @Column(name="isbn")
    @NotNull(message = "isbn is required")
    //@Size(min=8, max=8, message="isbn must be = 8 numbers")
    private Long isbn;

    @Column(nullable=false, name="title")
    @NotNull(message = "Title is required")
    private String title;

    @Column(nullable=false, name="edition")
    @NotBlank(message = "Edition is required")
    private String edition;

    @Column(nullable=false, name="price")
    @NotNull(message = "Price is required")
    private Double price;

    @Column(nullable=false, name="date_published")
    @Pattern(regexp = "^(0[1-9]|1[0-2])([\\/])([1-9][0-9])$", message = "Must be formatted MM/YY")
    private String datePublished;

    //@ForeignKey(name="FK_COUNTRY")
    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    @JoinColumn(name="author_id")//, referencedColumnName="id")
    @OnDelete(action = OnDeleteAction.CASCADE)
    private Author author;
}

我认为 book 表中的外键列将与 author 表的主键一起插入。

但是，如果我删除了指向作者主键的 referencedColumnName 属性，则会插入 null。

当我添加 referencedColumnName 属性时，出现错误，指示 null 无法插入到 book 表的外键列中。

java.sql.SQLIntegrityConstraintViolationException: ORA-01400: cannot insert NULL into ("SPRING"."BOOK"."AUTHOR_ID")

我创建了两个实体。

1. 作者(可以拥有/写很多书)[OneToMany]
2. 一本只能属于一位作者的图书 [ManyToOne]

当我在 Postman 中发送有效负载来测试插入 author 的 @PostMapping 时，book 表 (author_id) 中应引用 author 表主键 (id) 的外键将插入 null，而不是 author 主键的值。

当我添加 referencedColumnName 时，它会引发异常，指示 null 无法插入到 book.author_id 中。

我已经尝试过:

1. 使用@PrimaryKeyJoinColumn注释
2. referencedColumnName 属性

Answer 1

我能够通过添加两个注释来解决我的问题:JsonManageReference 和 JsonBackReference。

现场的@JsonManageReference私有(private)列出 Author 类中的书籍

和@JsonBackReference 在现场Book 类中的私有(private) Author 作者