@Override public final InputStream getInputStream() throws IOException {
    if (!doInput) {
      throw new ProtocolException("This protocol does not support input");
    }

    HttpEngine response = getResponse();

    // if the requested file does not exist, throw an exception formerly the
    // Error page from the server was returned if the requested file was
    // text/html this has changed to return FileNotFoundException for all
    // file types
//    if (getResponseCode() >= HTTP_BAD_REQUEST) {
//      throw new FileNotFoundException(url.toString());
//    }

    return response.getResponse().body().byteStream();
  }
Returns the value of the field corresponding to the {@code fieldName}, or
null if there is no such field. If the field has multiple values, the
last value is returned.
gateway/platforms/servlet/src/main/java/io/apiman/gateway/platforms/servlet/connectors/ok/HttpURLConnectionImpl.java