/** Ajax请求校验loginName是否唯一。 */
 @RequestMapping(value = "checkLoginName")
 @ResponseBody
 public String checkLoginName(@RequestParam("loginName") String loginName) {
   if (accountService.findUserByLoginName(loginName) == null) {
     return "true";
   } else {
     return "false";
   }
 }
 @RequestMapping(method = RequestMethod.POST)
 public String register(@Valid User user, RedirectAttributes redirectAttributes) {
   accountService.registerUser(user);
   redirectAttributes.addFlashAttribute("username", user.getLoginName());
   return "redirect:/login";
 }