@Override
 public List<UserCredit> getStarRankList(int limit) {
   return userCreditDao.getUserCreditList(limit, UserCredit.PROP_STAR_GRADE);
 }
 @Override
 public List<UserCredit> getPopRankList(int limit) {
   return userCreditDao.getUserCreditList(limit, UserCredit.PROP_VISITS);
 }
 @Override
 public List<UserCredit> getRichRankList(int limit) {
   return userCreditDao.getUserCreditList(limit, UserCredit.PROP_RICH_GRADE);
 }