The difference between your code and the code in the blog post is that you're calling em.persist() on the child object but the blog post is calling em.persist() on the parent object. If you want to take advantage of implicit entity group assignment it's important to manage children via their parents. If you switch em.persist(search) to em.persist(member) you should be fine.
Max On Wed, Dec 30, 2009 at 3:22 PM, Max Ross (Google) < maxr+appeng...@google.com <maxr%2bappeng...@google.com>> wrote: > I'd recommend basing your code on the example here to get something > working: > > http://gae-java-persistence.blogspot.com/2009/10/creating-bidrectional-owned-one-to-many.html > > Then you can start tweaking. > > Max > > > On Wed, Dec 30, 2009 at 3:02 PM, markm208 <markm...@gmail.com> wrote: > >> I am thoroughly confused… I am trying to set up a simple one to many >> relationship using JPA, I think that this should work but instead I >> get the error "Primary key for object of type Member is null." Any >> help would be greatly appreciated. >> >> @Entity(name = "Member") >> public class Member >> { >> @Id >> @GeneratedValue(strategy = GenerationType.IDENTITY) >> private Key id; >> >> @Basic //datastore specific type >> private Email memberEmail; >> private String memberPassword; >> private String memberFirstName; >> private String memberLastName; >> @Basic //blob of text not searchable >> private Text memberDescription; >> >> //Member 'owns' the Searches >> @OneToMany(mappedBy = "memberWhoCreated", cascade=CascadeType.ALL) >> private List < Search > searches = new ArrayList < Search >(); >> >> //getters and setters >> //... >> } >> >> @Entity(name = "Search") >> public class Search >> { >> @Id >> @GeneratedValue(strategy = GenerationType.IDENTITY) >> private Key id; >> >> private List < String > searchStrings; >> private boolean allowOthersToSee; >> @Basic //datastore specific type >> private Text contextOfSearch; >> >> @ManyToOne(fetch = FetchType.LAZY) >> private Member memberWhoCreated; >> >> public static Search createASearch(boolean allowOthersToSee, String >> context, Member member) >> { >> Search search = null; >> >> EntityManager em = null; >> try >> { >> //get the entity manager >> em = EMF.get().createEntityManager(); >> >> //create the search from the form variables >> search = new Search(); >> search.setAllowOthersToSee(allowOthersToSee); >> search.setContextOfSearch(new Text(context)); >> search.setMemberWhoCreated(member); >> >> em.getTransaction().begin(); >> try >> { >> >> //store the member >> em.persist(search); >> em.getTransaction().commit(); >> } >> finally >> { >> if (em.getTransaction().isActive()) >> { >> em.getTransaction().rollback(); >> } >> } >> } >> finally >> { >> em.close(); >> } >> >> return search; >> } >> >> //getters and setters >> //... >> } >> >> -- >> >> You received this message because you are subscribed to the Google Groups >> "Google App Engine for Java" group. >> To post to this group, send email to >> google-appengine-j...@googlegroups.com. >> To unsubscribe from this group, send email to >> google-appengine-java+unsubscr...@googlegroups.com<google-appengine-java%2bunsubscr...@googlegroups.com> >> . >> For more options, visit this group at >> http://groups.google.com/group/google-appengine-java?hl=en. >> >> >> > -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to google-appengine-j...@googlegroups.com. To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.
