Hi,
I'm trying to use default fetch groups to obtain fields at once (not
on demand) in my entity:
public class Survey {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
@Extension(vendorName="datanucleus", key="gae.encoded-pk",
value="true")
private String idSurvey;
@Persistent
private String name;
@Persistent
private Date dateFrom;
@Persistent
private Date dateUntil;
@Persistent
private String author;
@Persistent(mappedBy = "survey", defaultFetchGroup = "true")
private List<Response> responseList;
}
public class Response {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
@Extension(vendorName="datanucleus", key="gae.encoded-pk",
value="true")
private String idResponse;
@Persistent(defaultFetchGroup = "true")
private Survey survey;
//list of all Answers in this Response
@Persistent(mappedBy="response", defaultFetchGroup = "true")
private List<Answer> answerList;
}
I'm getting the entities with a method in a DAO class, so I need to
open and close the PM:
public Object getObjectByID(Class objectClass, String objectID) {
PersistenceManager pm = PMFactory.get().getPersistenceManager
();
Object o = null;
try {
o = pm.getObjectById(objectClass, objectID);
pm.retrieve(o);
} catch (JDOException jdoe) {
jdoe.printStackTrace();
} finally {
//pm.close();
}
return o;
}
When I fetch a Survey I can access the responseList and all fields in
Responses in the list. But when I fetch a Response, although I can see
the Survey (I'm using debugger in NetBeans to watch the variables),
every field of the Survey (except surveyID) is null, even if it has
been set before. So basically I can access child's fields after
obtaining the parent, but not via versa.
if I change the code in DAO to :
o = pm.getObjectById(Response.class, responseID);
pm.retrieve(o.getSurvey());
it works. Also, I could make it with not closing the PM - when the
fields are accessed they are being refreshed. What is happening? Thank
you!
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