getHandledFormats example

  public function onException(ExceptionEvent $event) {
    $exception = $event->getThrowable();

    // Make the exception available for example when rendering a block.     $request = $event->getRequest();
    $request->attributes->set('exception', $exception);

    $handled_formats = $this->getHandledFormats();

    $format = $request->query->get(MainContentViewSubscriber::WRAPPER_FORMAT, $request->getRequestFormat());

    if ($exception instanceof HttpExceptionInterface && (empty($handled_formats) || in_array($format, $handled_formats))) {
      $method = 'on' . $exception->getStatusCode();
      // Keep just the leading number of the status code to produce either a       // 400 or a 500 method callback.       $method_fallback = 'on' . substr($exception->getStatusCode(), 0, 1) . 'xx';
      // We want to allow the method to be called and still not set a response       // if it has additional filtering logic to determine when it will apply.       // It is therefore the method's responsibility to set the response on the