public FeedSubscription createSubscription(User user, String feedUrl, String feedTitle) throws NoSuchUserException, NotAuthorizedException, MissingIdException{
if(feedUrl == null || feedTitle == null){
throw new NullPointerException("either feedUrl or feedTitle is NULL");
}
GnizrDaoUtil.fillId(userDao, user);
Bookmark feedBmark = new Bookmark(user,new Link(feedUrl));
feedBmark.setTitle(feedTitle);
int bmId = bookmarkManager.addBookmark(feedBmark);
if(bmId <= 0){
logger.error("unable create bookmark: " + feedBmark);
}else{