code: protected void encodeFilterValues(final FacesContext context, final ResponseWriter responseWriter,
                  final Sheet sheet, final String clientId) throws IOException {
          int renderCol = 0;
          for (final SheetColumn column : sheet.getColumns()) {
              if (!column.isRendered()) {
                  continue;
              }
  
              if (column.getValueExpression("filterBy") != null) {
                  responseWriter.startElement("input", null);
                  responseWriter.writeAttribute("id", clientId + "_filter_" + renderCol, "id");
                  responseWriter.writeAttribute("name", clientId + "_filter_" + renderCol, "name");
                  responseWriter.writeAttribute("type", "hidden", null);
                  responseWriter.writeAttribute("value", column.getFilterValue(), null);
                  responseWriter.endElement("input");
              }
  
              renderCol++;
          }
      }
docs: Encodes the filter values.
  
  @param context
  @param responseWriter
  @param sheet
  @throws IOException