@RequestMapping(value = {"/login"},method = {RequestMethod.POST})
    public ResponseEntity<String> signIn(@RequestParam String account,
                                          @RequestParam String password){
        if(password==null||password.isEmpty()){
            return new ResponseEntity<>("password can't be null or empty",HttpStatus.BAD_REQUEST);
        }
        if(account==null||account.isEmpty()){
            return new ResponseEntity<>("account can't be null or empty",HttpStatus.BAD_REQUEST);
        }
        User user = userManager.getUserByAccount(account);
        if(user==null){
            return new ResponseEntity<>("User "+account+" not exists.",HttpStatus.BAD_REQUEST);
        }
        PasswordEncryptor passwordEncryptor = new BasicPasswordEncryptor();
        if(passwordEncryptor.checkPassword(password,user.getStringPassword())){
            return new ResponseEntity<>(HttpStatus.OK);
        }
        return new ResponseEntity<>("account or password error",HttpStatus.BAD_REQUEST);
    }