JSF - Pick List - Selected Values from picklist not propagating in backend bean

Question

I have a rich pick list component - selectedAOI is a List , aoiList is List;

In the UI, i can add the left hand side values to the right hand side but in the back end, once i submit the form , i am getting selectedAOI = null;

<rich:pickList value="#{bDataMgt.selectedAOI}" id="pkListAOI" listHeight="100" listWidth="100"
addAllText="&gt;&gt;" addText="&gt;" removeAllText="&lt;&lt;" removeText="&lt;" orderable="true" converter="#{bDataMgt.aoIdConverter}" > <f:selectItems value="#{bDataMgt.aoiList}"/> </rich:pickList>

The converter class :

public class AOIdConverter implements Converter{ @Override 
public Object getAsObject( FacesContext arg0, UIComponent arg1, String arg2 )
   {
      return arg2;
   }

   @Override
   public String getAsString( FacesContext arg0, UIComponent arg1, Object arg2 )
   {
      Long zoneId = (Long)arg2;
      return String.valueOf(zoneId);
   }
}

Can you please let me know where am i going wrong and how to populate the selected values in the picklist to the backend