public static void oauthTwitter() {
// first time the request comes here
// the user has just pushed the "sign in with twitter button"
if (!OAuth.isVerifierResponse()) {
final OAuth twitter = OAuth.service(TWITTER);
final OAuth.Response response = twitter.retrieveRequestToken();
if (response.error==null) {
final User user = new User();
user.token = response.token;
user.secret = response.secret;
user.save();
session.put("userId", user.id);
redirect(twitter.redirectUrl(response.token));
} else {
Logger.error("Error contacting twitter: " + response.error);
login();
}