class HttpResponseWrapper extends HttpServletResponseWrapper implements ResponseWithSessionId {

  @Override
  public SaveSessionServletOutputStream getOutputStream() throws IOException {
    if (writer != null) {
      throw new IllegalStateException("Only one of getWriter()/getOutputStream() can be called, and writer is already used.");
    }
    if (outputStream == null) {
      outputStream = wrapOutputStream(super.getOutputStream());
    }
    return outputStream;
  }

    HttpResponseWrapper(HttpRequestWrapper request, HttpServletResponse response);

}