code: private void encodeFooter(final FacesContext context, final ResponseWriter responseWriter, final Sheet sheet)
                  throws IOException {
          // footer
          final UIComponent footer = sheet.getFacet("footer");
          if (footer != null) {
              responseWriter.startElement("div", null);
              responseWriter.writeAttribute("class", "ui-datatable-footer ui-widget-header ui-corner-bottom", null);
              footer.encodeAll(context);
              responseWriter.endElement("div");
          }
      }
docs: Encode the sheet footer
  
  @param context
  @param responseWriter
  @param sheet
  @throws IOException