Question

i am using gwt with jdo datanucleus. i have requirement to get child with parent. but i am not getting child when access parent.
my code is as following

my parent class is

@PersistenceCapable(identityType = IdentityType.APPLICATION, table = "user")
public class User implements Serializable {

    private static final long serialVersionUID = 2660867968471555842L;

    @PrimaryKey
    @Persistent
    private String email;

    @Persistent(defaultFetchGroup = "true",mappedBy="user")
    private UserProfile profile;

    public User() {}

    public User(String email) {
        this.email = email;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public UserProfile getProfile() {
        return profile;
    }

    public void setProfile(UserProfile profile) {
        this.profile = profile;
    }
}

and my child class is

@PersistenceCapable(identityType = IdentityType.APPLICATION,table = "user_profile")
public class UserProfile implements Serializable {

    private static final long serialVersionUID = -6818036410894395030L;

    @PrimaryKey
    @Persistent(defaultFetchGroup="true")
    private User user;

    @Persistent
    private String name;

    public UserProfile() {}

    public UserProfile(User user) {
        this.user = user;
        user.setProfile(this);
    }

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

i am fetching data by following query

PersistenceManager pm = PMF.get().getPersistenceManager();
                 User user=null;

                try{
                    String userId ="[e-mail]";
                    Query userQuery = pm.newQuery(User.class);
                    userQuery.setFilter("email == '" + userId + "'");
                    userQuery.setUnique(true);
                    user = (User) userQuery.execute();
                } catch (Exception e) {
                    throw new IllegalAccessError("Failed to get the User..");
                }finally{
                    pm.close();
                }

but i am getting userprofile null in object user.
where is the problem ?
how to load children with parent ?

Answer 1

I’m not sure if you found your answer, but for those that stumble across this I just wanted to share how I got it working.

@PersistenceCapable(detachable = "true") 
@FetchGroup(name = "fooGroup", members = { @Persistent(name = "list") }) 
public class ParentClass {

    @Persistent(mappedBy = "parent")
    @Element(dependent = "true") //can not exist without parent
    private List<ChildClass> list;

}

@PersistenceCapable(detachable = "true") 
public class ChildClass {
    @Persistent
    private ParentClass parent;
}

and then to do the fetching:

PersistenceManager pm = PMF.get("eventual-reads-shortdeadlines").getPersistenceManager();
pm.setDetachAllOnCommit(true); 
pm.getFetchPlan().addGroup("fooGroup");
Transaction tx = pm.currentTransaction();

    try {
        tx.begin();

        Query query = pm.newQuery(ParentClass.class);
        list = (List<ParentClass>) query.execute();

        tx.commit();
    } catch (Exception ex) {
        ...
    } finally {
        if (pm != null) {
            if(pm.currentTransaction().isActive()){
                pm.currentTransaction().rollback();
            }
            pm.close();
        }
    }

Your ParentClass’s should now have all the ChildClass’s for each. Hope that helps!