/**
   * Convert the data to JSON and send it to the client.
   * 
   * @param req The client request.
   * @param resp The client response.
   * @param payload The data to convert to JSON and send.
   * @throws IOException
   */
  protected void sendResponse(
      HttpServletRequest req, 
      HttpServletResponse resp,
      Object payload
  ) throws IOException
  {
    if (payload == null) return;
    FilterProvider filters = new SimpleFilterProvider().addFilter("BaseEntity",new CanReadFilter());
    String json = getObjectMapper(req).filteredWriter(filters).writeValueAsString(payload);
    log.warning("json::".concat(json));
    log.warning("json size::"+json.length());
    resp.setContentLength(json.length());
    resp.setContentType("application/json");
    resp.getWriter().write(json);
    resp.flushBuffer();
  }