<af:commandButton text="Add Group"
action="#{backing_group_message_form.addGroupAction}"
useWindow="true"
returnListener="#{backing_group_message_form.handleAddingGroup}"
launchListener="#{backing_group_message_form.handleLaunchAddingGroup}"
partialSubmit="true"
immediate="true"/>

 public   void  handleAddingGroup(ReturnEvent event)
{
   Group retVal = (Group)event.getReturnValue();
    if  (retVal ==  null )
       return ;
   SelectItem si =  new  SelectItem();
   si.setValue(retVal.getGroupID());
   si.setLabel(retVal.getGroupName());
   groupVals.add(si);
}

 private  ArrayList<SelectItem> groupVals =  new  ArrayList<SelectItem>();