Can I keep available and seleted values in HashMaps for multiple Palette?

Question

Let's say I have loop like this:

<t:loop source="rolesToDisplay" value="selectedRole">
    <t:palette t:id="paletteSubjects" clientId="${prop:paletteSubjectsId}" model="availableSubjects.get(selectedRole)"
       selected="selectedSubjects.get(selectedRole)" encoder="stringValueEncoder"/>
</t:loop>

and I'm keeping some available and selected subjects (List<String>) for each role in HashMap<String, List<String>>.

This way I can view subjects for each role, but how can I update and submit values for ech role?

If I try change this to:

<t:loop source="rolesToDisplay" value="selectedRole">
    <t:palette t:id="paletteSubjects" clientId="${prop:paletteSubjectsId}" model="availableSubjects.get(selectedRole)"
       selected="selected" encoder="stringValueEncoder"/>
</t:loop>

with

public List<String> getSelected()
{
    return selectedSubjects.get(selectedRole);
}

public void setSelected(final List<String> sel)
{
    selectedSubjects.get(selectedRole).addAll(sel);
}

I got error on Submit: Parameter 'selected' of component user/Edit:palettesubjects is bound to null. This parameter is not allowed to be null.

I bet there is another way...

Answer 1

I'm not sure, but you possibly need to initialise the list for the first entry?

public List<String> getSelected() {
   if (!selectedSubjects.containsKey(selectedRole)) {
      selectedSubjects.put(selectedRole, new ArrayList<String>());         
   }
   return selectedSubjects.get(selectedRole);
}

public void setSelected(final List<String> sel) {
   List<String> selected = getSelected();
   selected.clear();
   selected.addAll(sel);
}