NPE on EM queries with no results; why?

[chris.simons]

Hi All,

I'm experiencing an issue running our Seam application; the issue deals with entityManager.createQuery wherein no results are returned.

Example:

result = (User)entityManager
            .createQuery(
                    "select poc.user from PointOfContact poc " +
                            "where poc.organization.id=:oid and poc.primary=true")
            .setParameter("oid", organization.getId())
            .getSingleResult();

Under JBoss AS and Hibernate/JPA, this query would return no results but this would be handled gracefully.

Now, under WebLogic (but ignore this fact, really, because it could happen under GlassFish or other JEE AS), I get a NullPointerException, such as:

]] Root cause of ServletException.
javax.ejb.EJBException: EJB Exception: : java.lang.NullPointerException
        at com.bah.englink.ejb.pm.SkillExperienceManager.lookupExperienceLevels(SkillExperienceManager.java:244)

If I catch the NPE, the application resumes normally.  But why the difference?  Since the returned value of this query is displayed using JSF EL, could that be the culprit?

Thanks.