Hello anonymous wrote : | It sounds like you want a ManyToMany relation. If Tasks can have many TaskItems and a TaskItem can be associated with more than one Task this is a ManyToMany relation, not a OneToMany. | Hmm but the TaskItem dont have any information about the task it owns (no getTask() method) and its not biderectional.I shoudl learn sth about database design. Thx for giving me the right hint i changed my code to: | @ManyToMany( | targetEntity=TaskItem.class, | cascade={CascadeType.PERSIST, CascadeType.MERGE} | ) | @JoinTable( | name="task_taskItems", | joinColumns = { @JoinColumn( name="task_id", unique = false)}, | inverseJoinColumns = @JoinColumn( name="taskItem_id", unique = false) | ) | and now its working - no complaining anymore about duplicated entry. Thank u very much, helped me a lot and sorry for posting in wrong forum. Bye, Holger View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3961449#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...