How do I catch the constraint violation exception from EclipseLink?

Question

I am using EclipseLink in my web application, and I am having a hard time gracefully catching and handling Exceptions it generates. I see from this thread what seems to be a si

Answer 1

It looks like I won't get any more activity on this question, so I will post my work-around and leave it at that. A number of web searches haven't found much of anything that is helpful. I would have thought this is a textbook case but none of the tutorials I have found covers it.

As it turns out in this condition with EclipseLink, the Exception you can catch when the SQL constraint is violated is the RollBackException that is the result of the em.commit() call. So I have modified my persist method like this:

public void persist(Category category) throws EntityExistsException {
    try {
        utx.begin();
        em.persist(category);
        utx.commit();
    } catch (RollbackException ex) {
        Logger.getLogger(CategoryControl.class.getName()).log(Level.SEVERE, null, ex);
        throw new EntityExistsException(ex);
    } catch (HeuristicMixedException ex) {
        Logger.getLogger(CategoryControl.class.getName()).log(Level.SEVERE, null, ex);
    } catch (HeuristicRollbackException ex) {
        Logger.getLogger(CategoryControl.class.getName()).log(Level.SEVERE, null, ex);
    } catch (SecurityException ex) {
        Logger.getLogger(CategoryControl.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IllegalStateException ex) {
        Logger.getLogger(CategoryControl.class.getName()).log(Level.SEVERE, null, ex);
    } catch (NotSupportedException ex) {
        Logger.getLogger(CategoryControl.class.getName()).log(Level.SEVERE, null, ex);
    } catch (SystemException ex) {
        Logger.getLogger(CategoryControl.class.getName()).log(Level.SEVERE, null, ex);
    }
}

So the caller catches the EntityExistsException and takes the appropriate action. The log still fills up with the internal exceptions but that can be shut off later.

I realize that this is a bit of an abuse of the intent of the EntityExistsException that is normally only used when an entity ID field is re-used, but for the purposes of the user application it doesn't matter.

If anyone has a better approach please post a new answer or comment.