Question

我试图创建存储库方法，以便我可以在访问本书所有作者的详细信息时显示（反之亦然）。它的多对多关系，模型类看起来像这样：

作者（模特）课程：

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

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "author_id")
    private int authorId;
    @Column(name = "name")
    private String name;
    @Column(name = "surname")
    private String surname;
    @Column(name = "date_of_birth")
    private Date dateOfBirth;

    @Column(name = "alive")
    private boolean alive;

    @ManyToMany(cascade = CascadeType.ALL, mappedBy="authors")
    @JoinTable(name = "book_author",
            joinColumns = @JoinColumn(name = "book_id"),
            inverseJoinColumns = @JoinColumn(name = "author_id"))
    private Set<Book> books = new HashSet<Book>();

预订（模特）课程

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

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "book_id")
    private int bookId;
    @Column(name = "isbn")
    private long isbn;
    @Column(name = "title")
    private String title;
    @Column(name = "title_original")
    private String titleOriginal;
    @Column(name = "premiere_date")
    private Date premiereDate;
    @ManyToMany(cascade = CascadeType.ALL, mappedBy="books")
    @JoinTable(name = "book_author", joinColumns = { @JoinColumn(name = "book_id") }, inverseJoinColumns = { @JoinColumn(name = "author_id") })
    private Set<Author> authors = new HashSet<Author>(0);

BookRepository 类：

@Repository
public interface BookRepository extends CrudRepository<Book, Integer> {

    List<Book> findByIsbn(@Param("isbn") long isbn);
    List<Book> findByTitle(@Param("title") String title);
    List<Book> findByTitleOriginal(@Param("titleOriginal") String titleOriginal);
    @Query("SELECT b FROM Book b WHERE b.premiereDate BETWEEN :startYear AND :endYear ORDER BY b.premiereDate")
    public List<Book> getBooksBetweenDate(@Param("startYear")int startYear, @Param("endYear")int endYear);




@Query("SELECT b FROM Book b JOIN b.authors a WHERE a.authorId =:idAuthor")
public List<Book> getBookAuthors(???)

我认为我的模型类和存储库中的hql查询都可以，但我不知道如何创建方法 getBookAuthors 。

提前感谢您的帮助。

Answer 1

您需要在一侧（拥有实体端）指定连接表，并在另一侧指定mappedBy，例如在Book实体中

  @ManyToMany(cascade = CascadeType.ALL. mappedBy="books")
   private Set<Author> authors = new HashSet<Author>(0);

所以现在你在书和作者之间存在双向关系，如果你想要检索一本书的作者，你只需要使用你的存储库检索这本书，然后找到它的作者

 Book book = BookRepository.findOne(bookId);//bookId contains the id of your book
Set<Author> authors = book.getAuthors();//im supposing you have getter for your authers in Book class

HQL多对多的存储库方法

1 个答案: