PickList lose value - primefaces

Question

I have a simple persistent object (Hibernate, if it makes any different):
#Entity
Class ObjectA
{
private Long id;
private String name;
private String description;
private List<ObjectA> children = new LinkedList<>();
...
...
...
public org.primefaces.model.DualListModel<ObjectA> getDualList() {
org.primefaces.model.DualListModel<ObjectA> l = new org.primefaces.model.DualListModel<>();
l.setSource(this.children);
l.setTarget(database.getAllChildren()); // performs database query to retrieve all objectA that are not corrently linked to any objectA.
...
return l;
}
public setDualList(org.primefaces.model.DualListModel<ObjectA> l) {
this.children = l.getSource();
...
}
}
The PrimeFaces code looks like (relevant snippet):
...
<p:dataTable id="table" value="#{managedBeanA.getAllObjects}" var="iterator" paginator="true" rows="10" >
...
...
<p:rowExpansion>
<p:pickList value="#{iterator.dualList}" var="l" itemLabel="#{l.name}" itemValue="#{requirement.id}">
<f:facet name="sourceCaption">Linked Children</f:facet>
<f:facet name="targetCaption">Unlinked Children</f:facet>
<p:ajax event="transfer" listener="#{managedBeanA.handleTransfer(iterator)}"/>
</p:pickList>
</p:rowExpansion>
</p:dataTable>
What managedBeanA.handleTransfer does is simply persist the passed object.
Everything seems to work lovely, I can expand the row and getDualList is called. When I expand another row, another getDualList is called - all as expected.
When I move items from source to target, managedBeanA.handleTransfer is called and the relevant object is persisted in the database.
HOWEVER, and here is the question, when the table is updated - either form submit or ajax, I can see that setDualList is called for EVERY item in the p:dataTable with EMPTY getSource which, in essence, break all the links previously persisted (i.e. this.children = null). The previously linked ObjectA objects are still in database but they are no longer linked...
Any ideas what is going on?

Answer 1

I have found a solution to the problem. It is probably only a workaround as I am not sure what the problem actually is - in the setDualList method, I have added the following line:
if (l.getSource().isEmpty() && l.getTarget().isEmpty()) return;
which solves all my problems (as the symptom of the issues is that the setter is called with no values).