code: @Override
      public void doFilter(ServletRequest req, ServletResponse resp, final FilterChain chain) throws IOException,
          ServletException {
  
          if (manager == null || isHttpRequest(req, resp)) {
              doFilterHttp((HttpServletRequest) req, (HttpServletResponse) resp, chain);
          } else {
              chain.doFilter(req, resp);
          }
      }
docs: Detects whenever the request is HTTP request and if yes, delegates to
  {@link #doFilterHttp(HttpServletRequest, HttpServletResponse, FilterChain)}.