@Override
 public String getAccountByAccessToken(String accessToken) {
   OAuthObject authObject = (OAuthObject) cache.get(accessToken).get();
   return authObject == null ? null : authObject.getAccount();
 }
 @Override
 public String getAccountByAuthCode(String authCode) {
   OAuthObject authObject = (OAuthObject) cache.get(authCode).get();
   return authObject == null ? null : authObject.getAccount();
 }