src/Service/Keeper.php
public function getModifiedResponse(Request $request, $params = [], $lifetime = -1, Response $response = null)
    {
        $response = $this->getResponse($params, $lifetime, $response);

        if ($response->isNotModified($request)) {
            throw new NotModifiedException($response);
        }

        return $response;
    }
public function getModifiedResponse(Request $request, $params = [], $lifetime = -1, Response $response = null)
    {
        $response = $this->getResponse($params, $lifetime, $response);

        if ($response->isNotModified($request)) {
            throw new NotModifiedException($response);
        }

        return $response;
    }
Get only modified response.

Throw exception if response was not modified for this request

Set $lifetime as < 0 for not set max-age

@throws NotModifiedException

@param Request $request
@param mixed $params
@param int $lifetime
@param Response|null $response

@return Response