SpringJPA一对多关联，外键插入NULL

今早起床后想验证一下jpa OneToMany注解。 写了demo， 主实体，也就是One对应的一方和从实体，也就是Many对应的实体数据都插入数据库了，但是在多的一方外键id插入NULL， 查询了一下，是使用上的问题

两个实体

@Entity
@Table(name = "Book")
@Setter
@Getter
public class Book implements Serializable {

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

    @Column(name = "BookName")
    private String bookName;

    @Column(name = "Isbn")
    private String isbn;
 
    //这里我维护了一本书可以由多个出版商负责
    @OneToMany(mappedBy = "book", cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<Publisher> publisherList = new ArrayList<>();
}
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@Entity
@Table(name = "Publisher")
@Setter
@Getter
public class Publisher implements Serializable {

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

    private String publisherName;

    public Publisher(){}

    @ManyToOne
    @JoinColumn(name = "BookId")
    private Book book;
}
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客户端调用

public static void main(String[] args) {
    ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);

    DataSource dataSource = context.getBean(DataSource.class);
    System.out.println("DataSource:"+dataSource.getClass().getName());


    Book book = new Book();
    book.setBookName("java从入门到放弃");
    book.setIsbn("1");

    Publisher publisher = new Publisher();
    publisher.setPublisherName("清华出版社");
    //这里要设置book属性， 否则publisher表BookId外键是NULL
    publisher.setBook(book);
    
    //这里要使用getPublisherList.add() 
    //如果上面先new一个ArrayList， 在这里用book.setPublisherList(...) 数据也不生效
    book.getPublisherList().add(publisher);

    BookRepository bookRepository = context.getBean(BookRepository.class);
    bookRepository.save(book);

}
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