麻烦大家帮我看看为什么执行如下代码后，更改的数据无法保存到数据库中，这是为什么呢？

//修改信息，真正添加到数据库 updateInfo
public ActionForward updateInfo(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) {

    //将字符串转化为日期类型
    DateFormat format = new SimpleDateFormat("yyyy-MM-dd");

    //得到当前用户[从session取出]
    Users loginUser = (Users) request.getSession().getAttribute("loginuser");

    //从表单中获取修改个人的信息(birth,tel,website,msn,book,movie,music,sport,cartoon)
    UserForm userForm = (UserForm)form;

    try{
        loginUser.setBirth(format.parse(userForm.getBirth()));
    }catch(ParseException e){
        e.printStackTrace();
    }
    loginUser.setTel(userForm.getTel());
    loginUser.setWebsite(userForm.getWebsite());
    loginUser.setMsn(userForm.getMsn());
    loginUser.setBook(userForm.getBook());
    loginUser.setMovie(userForm.getMovie());
    loginUser.setMusic(userForm.getMusic());
    loginUser.setSport(userForm.getSport());
    loginUser.setCartoon(userForm.getCartoon());

    //保存用户
    userService.save(loginUser);

    return mapping.findForward("goHomePageUI");
}