code: @Override
      public void sendError(int code, String message) throws IOException {
          if (isCommitted()) {
              throw new IllegalStateException("Response already committed");
          }
          resetBuffer();
          this.response.setStatus(code);
          commit();
          if (null != message) {
              if (null != this.outWriter) {
                  this.outWriter.print(message);
              } else {
                  this.outStream.print(message);
              }
              flushBuffer();
          }
      }
docs: /*
  @see javax.servlet.http.HttpServletResponse#sendError(int, java.lang.String)