Hi, i may find something here http://code.google.com/intl/en/appengine/docs/java/datastore/relationships.html
[]'s Diego On 26 ago, 04:42, cghersi <[email protected]> wrote: > Hi everybody, > > I'm struggling with a strange problem with JDO. > I've got two PersistenCapable classes, one having a Collection of > objects of the second, something like this: > > class First { > �...@persistent > �...@primarykey > Long id; > > �...@persistent(mappedby="owner") > ArrayList<Second> list = new ArrayList<Second>(); > > ArrayList<Second> getList() { > if (list == null) > list=new ArrayList<Second>(); > return list; > } > > ... > > } > > class Second { > �...@persistent > �...@primarykey > Key id; > > �...@persistent > First owner; > > First getOwner() { > if (owner==null) > owner = new First(); > return owner; > > ... > > } > > In another class I need to print the owner of all my First objects, so > I do: > First obj = ...; > ArrayList<Second> list = obj.getList(); > for (Second s : list) { > System.out.println(s.getOwner()); > > } > > In this loop, I find some Second object having null owner, and I > cannot understand why. > Now I have several questions about my data modelling: > 1) Do I need to mark any field with (defaultFetchGroup = "true") > annotation? > 2) Does the check on null object (e.g. if (owner==null) owner = new > First();) in the getter methods results in any strange behavior? > 3) Does the assignment on definition of objects (e.g. > ArrayList<Second> list = new ArrayList<Second>();) results in any > strange behavior? > 4) Do I need to add any other annotation to owner field of Second > class? > > Thank you very much for your help!! > Best regards > cghersi -- 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 [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.
