Question

我正在尝试在2个表之间实现单向多对多关系，如下所示：

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

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

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

 @ManyToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "book_author", 
             joinColumns = { @JoinColumn(name = "book_id") }, 
             inverseJoinColumns = { @JoinColumn(name = "author_id") })
private List<Author> bookAuthors;
  //getter and setters here
 }

我的作者课程如下：

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

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

@Column(name="author_name")
private String authorName;

@Column(name="author_description")
private String authorDesc;
//getter setters here
}

用于保存数据的代码如下（请注意，我要在拥有实体的book对象上调用save）：

   //create book
    Book book1 = new Book();
    book1.setBookName("Book1");

    //create and set Author info
    Author author1 = new Author();
    author1.setAuthorName("a1");
    author1.setAuthorDesc("a1 description");

    Author author2 = new Author();
    author2.setAuthorName("a2");
    author2.setAuthorDesc("a2 description");

    List<Author> authorsList1 = new ArrayList<Author>();
    authorsList1.add(author1);
    authorsList1.add(author2);
    book1.setBookAuthors(authorsList1);


    //save book
    session.save(book1);

这将执行以下休眠代码：

Hibernate: insert into Book (book_name, category_id, numOfCopies) values (?, ?, ?)
Hibernate: insert into Author (author_description, author_name) values (?, ?)
Hibernate: insert into Author (author_description, author_name) values (?, ?)

查询表时，我在Book and Author表中看到数据，但在联接表中看不到数据，即Book_author。知道我做错了什么吗？

我提到了以下示例： http://websystique.com/hibernate/hibernate-many-to-many-unidirectional-annotation-example/

我什至尝试通过将书籍添加到作者类中来将代码更改为双向映射，如下所示：

@ManyToMany(mappedBy="bookAuthors")
private List<Book> books;

，但是仍然没有数据保存到联接表中。

任何帮助将不胜感激！

谢谢！

Hibernate单向多对多不插入联接表

0 个答案: