我有一个身份验证过滤器，在这里处理身份验证请求时，我应该发送一个post请求/登录，主体为{“username”：“asdd”，“password”：“asada”}

@RequiredArgsConstructor
public class JsonAuthenticationFilter extends UsernamePasswordAuthenticationFilter {

private final ObjectMapper objectMapper;

@Override
public Authentication attemptAuthentication(HttpServletRequest request, HttpServletResponse response) {

  if (isJsonContent(request)) {
    return authenticate(request);
  }

  return super.attemptAuthentication(request, response);
}

private boolean isJsonContent(HttpServletRequest request) {
  try {
    String contentType = request.getContentType();
     return !isEmpty(contentType) && APPLICATION_JSON.isCompatibleWith(parseMediaType(contentType));
 } catch (InvalidMediaTypeException e) {
  return false;
  }
}

private Authentication authenticate(HttpServletRequest request) {
  val login = readRequest(request);

  UsernamePasswordAuthenticationToken authToken = new UsernamePasswordAuthenticationToken(login.username, 
  login.password);

  setDetails(request, authToken);

  return this.getAuthenticationManager().authenticate(authToken);
}

private LoginRequest readRequest(HttpServletRequest request) {
  ...
  return new LoginRequest(username, password)
}

@Value
private static class LoginRequest {
  String username;
  String password;
  }
}

在这里，我捕获auth失败并返回带有自定义消息的json

@Component
@AllArgsConstructor
@FieldDefaults(level = PRIVATE, makeFinal = true)
public class CustomAuthenticationFailureHandler
implements AuthenticationFailureHandler {

@NonNull
ObjectMapper objectMapper;

@NonNull
AccountRepository userRepository;

@Override
@ResponseBody
public void onAuthenticationFailure(
HttpServletRequest request,
HttpServletResponse response,
AuthenticationException exception) throws IOException {

  String username = request.getParameter("username"); <-- and here its returns null!!

  request.getUserPrincipal();
  Account account = userRepository.findByLogin(username);

  String errorCode = checkAccount(account);

  response.setStatus(HttpStatus.UNAUTHORIZED.value());
  response.setContentType(MediaType.APPLICATION_JSON_VALUE);
  response.setCharacterEncoding(StandardCharsets.UTF_8.toString());
  objectMapper.writeValue(response.getWriter(), new ValidationErrors(exception, errorCode));
}

private String checkAccount(Account account) {
  ....
  return errorCode;
  }
}

问题是我无法从请求中获取用户名。也许我把它过滤掉了？如何从请求中获取用户名？也许我忘了用用户名和密码设置一些参数？