Hello everybody!
I have basic question. Unfortunately, I couldn't find clear answer.
I was playing with annotations example from "Beginning Hibernate" book.
The model has several classes, two of them have many to many relationship:

something like this:
class Book {
...
@ManyToMany
Set<Author> authors;
}

class Author {
...
@ManyToMany
Set<Book> books;
}

then they create two books, two authors and add authors to books:

Book b1 = new Book();
Book b2 = new Book();

Author a1 = new Author();
Author a2 = new Author();

b1.authors.add(a1);
b1.authors.add(a2);
b2.authors.add(a1);
b2.authors.add(a2);

and finally call
session.save();

Everything is fine in database, if I open new session and get all objects I see each book has two authors and each author has two books.
But right after session.save() the model is inconsistent- each book has two authors but each author has empty set of books.
It looks very strange, after save() operation all objects are controlled by hibernate, I would expect consistent model.
What do I miss?

Thank you,
Andrey

you also need to add the books to author's book-collections. hibernate does not do that for you on save. if you open another session and read the objects from the database the object-model is consistent.