code: public void setRowVar(final FacesContext context, final String rowKey) {
  
          if (context == null) {
              return;
          }
  
          if (rowKey == null) {
              context.getExternalContext().getRequestMap().remove(getVar());
          }
          else {
              final Object value = getRowMap().get(rowKey);
              context.getExternalContext().getRequestMap().put(getVar(), value);
          }
      }
docs: Updates the row var for iterations over the list. The var value will be updated to the value for the specified rowKey.
  
  @param context the FacesContext against which to the row var is set. Passed for performance
  @param rowKey the rowKey string