问Symfony REST API的响应缓存

EN

public function postProductsAction(Request $request)
{

    $em = $this->get('doctrine')->getManager();

    // TODO check if db is unchanged and cache exists
    // if check is true stop here and redirect to cached json response

    $products = $em->getRepository('PPApiBundle:Produkte')->findBy(array("status" => 1));

    $data = array(
      "data" => $products,
      "opt" => array()
    );

    $view = $this->view($data, 200);
    $ret = $this->handleView($view);

    // TODO cache json string after serialization 

    return $ret

}