[jboss-user] [EJB 3.0] - Using own Classes as member for ManyToMany-Assotiations

I defined a class public class UsergroupList extends ArrayList<Usergroup> | {} | The class user is public class User implements Serializable | { ... | private UsergroupList mUsergroupList; | | @ManyToMany ( targetEntity = Usergroup.class ) | public Collection getUsergroupList() | { return mUsergroupList; } when deploying I get the error org.hibernate.AnnotationException: Illegal attempt to map a non collection as a @OneToMany, @ManyToMany or @CollectionOfElements: com.xyz.UsergroupList | but I think UsergroupList implements collection as it is an ArrayList If I write @ManyToMany ( targetEntity = Usergroup.class ) | public Collection getBenutzerGruppeListe() | { return mUsergroupList; } | the deployment works. But invoking private EntityManager em; | ... | erg = (List<User>) em.createQuery("from User").getResultList(); | throws javax.ejb.EJBException: javax.persistence.PersistenceException: org.hibernate.PropertyAccessException: Exception occurred inside setter of com.xyz.User.usergroupList | View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4011917#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...