EJB 3.0 and ManyToMany relationship

[Gerald Holl]

I have problems with ManyToMany relationships in EJB 3.0 (JBoss 4.0.3RC1)

Consider the following example:

class Book:

private String bookName; // PK
private Set<BookAuthor> authors;
 
...
 
@ManyToMany(cascade = { CascadeType.PERSIST, CascadeType.MERGE }, mappedBy = "books")
public Set<BookAuthor> getAuthors() {
  return authors;
}
 
public void setAuthors(Set<BookAuthor> authors) {
  this.authors = authors;
}

class BookAuthor:

private String author; // PK
private Set<Book> books;
 
...
 
@ManyToMany(cascade = { CascadeType.PERSIST, CascadeType.MERGE })
@JoinTable(table = @Table(name = "BookAuthorMapping"), joinColumns = { @JoinColumn(name = "author") }, inverseJoinColumns = { @JoinColumn(name = "book") })
public Set<Book> getBooks() {
  return books;
}
 
public void setBooks(Set<Book> books) {
  this.books = books;
}

I don't know how to add a book and it's author.
If I add a book do I have to create a Set that holds all the authors? And do I have to add that book to the books Set of the author bean?
I have absolutely no idea how this works. I didn't find a good tutorial (not even on the JBoss website) with google.

Hope that somebody can explain me how it works.

Thanks,
Gerald

[Haibo Wang]

i advise u read <<hibernate in action >>
it is a good bible and u will find more detailed discription for your question.

[Mike Keith]

Gerald,

Here is another EJB 3.0 preview that has tutorials and will help you
learn how to use EJB 3 mappings:

http://www.oracle.com/technology/tech/java/ejb30.html

Try that out.

-Mike

BTW, Haibo, Hibernate in Action has nothing to do with EJB 3.