I was reading this post"
http://www.datanucleus.org/products/accessplatform_1_1/jdo/fetchgroup.html
" about fetch group because I encountered problem in accesseing a
List<Evaluation> field when I use pm.getObjectbyID(Course.class,
myKey), in which Course contains a List<Evaluation> field
So I change Course as follows:
@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class Course {
...
@Persistent(defaultFetchGroup="true", mappedBy = "course")
private List<Evaluation> evaluations;
...
}
Now problem is solved but there's a warning
WARNING: Meta-data warning for data.Course.evaluations: The datastore
does not support joins and therefore cannot honor requests to place
related objects in the default fetch group. The field will be fetched
lazily on first access. You can modify this warning by setting the
datanucleus.appengine.ignorableMetaDataBehavior property in your
config. A value of NONE will silence the warning. A value of ERROR
will turn the warning into an exception.
I am now looking for where the meta-data I could make change to solve
this problem. Can anyone help me on this?
One more question is I don't understand what "fetched lazily" means in
the warning. In fact I don't encountered any problems if I use
pm.newQuery() in getting the List<Evaluation> field. only
pm.getObjectbyID() cause me errors.
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