Serialization of detached JDO's in gwt's RemoteService Implementation

Question

In my RemoteServiceImpl (gwt) i would return an ArrayList. The model has a few members referencing to other objects which are also persistable. The whole object tree comes from gae datastore. I have to detach the objects before returning them in RemoteServiceImpl. Unfortunately after invoking pm.detachCopy() the nested information is lost which was previously present.

@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable = "true")
@FetchGroup(name = "wc", members = {@Persistent(name = "waterConditions",
    recursionDepth =  -1)})
@JsonSerialize(include = JsonSerialize.Inclusion.NON_EMPTY)
public class InventoryInhabitant implements Serializable {
    ...
    @Persistent(defaultFetchGroup = "true")
    @Element(dependent = "true")
    private InventoryWaterConditions waterConditions;
    ....
}

@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable = "true")
@JsonSerialize(include = JsonSerialize.Inclusion.NON_EMPTY)
public class InventoryWaterConditions implements Serializable {
    ...
    @Persistent(defaultFetchGroup = "true")
    @Element(dependent = "true")
    private InventoryPh ph;
    ...
}

Getter and Setter present just omitted for brevity. After detaching the field waterConditions is not null but it contains nothing all members for example "ph" are null.

What i am do wrong in my case?

Answer 1

The PersistenceManager has a FetchPlan. A FetchPlan has a maximum "fetch depth" which you can set following this link http://www.datanucleus.org/products/accessplatform_4_0/jdo/fetchgroup.html