class PushNotificationSubscriptionServiceImpl implements PushNotificationSubscriptionService {

    @Nonnull
    @Override
    public PushNotificationSubscription getPushNotificationSubscriptionForUser(@Nonnull final Long userId) {
        assertUserIdNotNull(userId);
        LOGGER.debug("Getting push notification subscription for user with id - {}", userId);
        final User user = userService.getUserById(userId);
        final PushNotificationSubscription subscription = pushNotificationSubscriptionRepository.findByUser(user);
        assertPushNotificationSubscriptionNotNullForUser(subscription, user);
        LOGGER.debug("Successfully retrieved push notification subscription for user with id - {}, subscription - {}", user.getId(), subscription);
        return subscription;
    }

    public  PushNotificationSubscriptionServiceImpl();

}