Question

I set up a Database Application with Spring an Hibernate and I’m using a Many-To-Many-Relationship.
Here’s the code:

Author.java

@ManyToMany(cascade = {CascadeType.ALL})
@JoinTable(name = "writes", joinColumns = {@JoinColumn(name = "authorId")}, inverseJoinColumns = {@JoinColumn(name = "publicationId")})
private Set<Publication> publications = new HashSet<Publication>();

Publication.java

@ManyToMany(mappedBy = "publications")
private Set<Author> authors = new HashSet<Author>();

these lines of code generate a connection-table named writes, but when I try to run a query over all Tables int gives me the error, named above.

this is the method, that schould run the query:

@Transactional
public List<Author> findAuthorByLastname(String lastName) {
    String hql = "from Author a, Publication p, writes w where a.id = w.authorId and p.id = w.publicationId and a.lastname = :lastName";
    Query q = sessionFactory.getCurrentSession().createQuery(hql);
    q.setParameter("lastName", lastName);
    List<Author> result = q.list();
    return result;
}

Answer 1

You don’t need to mention connection table explicitly in HQL queries (moreover, you even cannot mention them – only mapped entities). You need to use join on mapped relationships instead.

Also, it’s not quite clear what you want to achieve.

• If you want to fetch Authors with eagerly filled collections of their Publications in one query, use join fetch:

  select distinct(a) from Author a join fetch a.publications where a.lastName = :lastName
  

• If you want to fetch a list of pairs (Author, Publication), use regular join:

  select a, p from Author a join a.publications p where a.lastName = :lastName