Simple JPA - JSF question

Question

Welcome!
I Have simple question regarding updating JPA entities from JSF application
One option is to directly invoke entity manager code from JSF managed bean action, but in this case we must explicitly deal with transactions (and we don't get other EJB benefits).
Other approach is to create EJB as a stateless session bean. And delegate all the operations on entities to the EJB. In this case container create transactions for us.
Please correct me if I wrongly understand this topic.
My key question is how to update entity bean, which I have persiteted earlier. I assume it's illegal to issue manager .find method in EJB class, return managed entity as an object to JSF backing been and then modify it. Normally entity bean should be managed, but in this case there is no transaction support in JSF backing bean and hence we cannot modify the object directly.
I assume that correct way is to detach entity in EJB, pass this object to JSF backing bean. In this case entity will not be managed, then edit it in JSF and finally update in EJB by .merge method.
I assume multi-user environment (currently I am using glassfish if it does matters)
Best regards
Pawel

Answer 1

Thanks for responding r035198x (this place has some memorable usernames :) ).
You were absolutely right about flagging me up for not catching the exception (at the time I didn't know how to handle exceptions as im still learning). I am now using:
FacesContext.getCurrentInstance().addMessage(null, new FacesMessage("Error deleting record: "+ex.getMessage()));and am now getting the following when pressing the delete button:
Error deleting record: Internal Exception: java.sql.SQLIntegrityConstraintViolationException: DELETE on table 'MBUSER' caused a violation of foreign key constraint 'USERPOST_OWNER_ID' for key (4). The statement has been rolled back. Error Code: -1 Call: DELETE FROM MBUSER WHERE (ID = ?) bind => [4] Query: DeleteAllQuery(name="messageboard.entity.MBUser.deleteUser" referenceClass=MBUser sql="DELETE FROM MBUSER WHERE (ID = ?)")
This is probably getting out of the realm of JSF, but in case your interested I can delete a user which does not have any child posts or threads (this is a messageboard), but if that user owns any threads or posts then it shows the above error. At this stage I am guessing its because I am not deleting joined child objects which are in persistence, and therefore will not allow the parent to be deleted without first the children being deleted. I was hoping that the cascade tag in the @OneToMany annotation would do it for me, but that doesn't seem to be the case:
    @OneToMany(mappedBy = "owner", cascade = CascadeType.ALL)
    private List<UserPost> ownedPosts = null;
    @OneToMany(mappedBy = "owner", cascade = CascadeType.ALL)
    private List<UserThread> ownedThreads = null;Therefore I guess i'll have to construct a NamedQuery a bit more complicated than the current one im using. Still, at least im making progress :) Thanks...