list列表数据为空

public List<Users> UsersLogin(String userName,String passWord){

BaseDao bd = new BaseDao();

Users u = new Users();

u.setUserName(userName);

u.setUserPassword(passWord);

List<Users> list = new ArrayList<Users>();

SqlSession sqlSession = null;

try {

sqlSession = bd.getSqlSession();

list = sqlSession.selectList("userLogin",u);

} catch (IOException e) {