HQL 多对多存储库方法

Question

我正在尝试创建存储库方法，以便在访问书籍的所有作者的详细信息时显示（反之亦然）。这是多对多的关系，模型类看起来像这样：

作者（模型）类：

@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>();

图书（模型）类

@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 查询没问题，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（拥有实体一侧）指定连接表并在另一侧指定 mappedBy，例如在您的 Book 实体中

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

现在您在书籍和作者之间建立了双向关系，如果您想检索一本书的作者，您只需使用您的存储库检索该书，然后获取其作者

 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