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Hibernate: insert ManyToMany, generate ID in relationship table
class Books
{
   @Id
   long id;

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


   @ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
   @JoinTable(name = "BOOKS_AUTHORS",
              joinColumns = @JoinColumn(name = "book_id"),
              inverseJoinColumns = @JoinColumn(name = "author_id"))
   List<Authots> authors;

// setter, getters, adder
}

class Authors
{
   @Id
   long id;

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

   @ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
   @JoinTable(name = "BOOKS_AUTHORS",
              joinColumns = @JoinColumn(name = "author_id"),
              inverseJoinColumns = @JoinColumn(name = "book_id"))
   List<Books> books;

// setter, getters, adder
}

public void addAuthor(final String bookName, final Author author)
{
      final Book book = // get book from database by bookName
      if (book == null)
         throw new DataNotFoundException("Book not found :(");
      author.addBook(book);
      book.addAuthor(author);
      entityManager.persist(author);
}

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;

ALTER table book_authors CHANGE id long NOT NULL AUTO_INCREMENT;

session.CreateCriteria(typeof (BOOKS_AUTHORS))
                           .SetProjection(Projections.Max("Id"))
                           .UniqueResult()