@Override
 public Bidder findByEmail(String email) {
   Bidder binder = null;
   try {
     binder = bidderDao.findByColumns(new String[] {"email"}, new Object[] {email});
   } catch (EmptyResultDataAccessException t) {
     log.warn("投標者不存在", t);
   }
   return binder;
 }
 @Override
 public Bidder findById(Long bidderId) {
   Bidder binder = null;
   try {
     binder = bidderDao.findById(bidderId);
   } catch (EmptyResultDataAccessException t) {
     log.warn("投標者不存在", t);
   }
   return binder;
 };
 public List<Bidder> findAll() {
   return bidderDao.findAll();
 }