Flutter调用用户创建API成功却返回500错误，请求帮助

我是Dio新手，在Flutter中调用API创建新用户时遇到问题：调用createUser()函数后，后端已成功创建用户，但Dio抛出状态码为500的DioError。切换到http库调用，仍出现相同的500错误。

一、Dio实现代码 #

Future<User> createUser({
  required String email,
  required String username,
  required String password,
  required String password2,
}) async {
  BaseOptions options = BaseOptions(
    baseUrl: 'https://XXXXXX.XXXX.com',
  );
  final Dio dio = Dio(options);

  Response? response;
  try {
    response = await dio.post(
      '/signup_person',
      data: {
        'email': email,
        'username': username,
        'password': password,
        'password2': password2
      },
    );
    print('Request completed');
  } on DioError catch (e) {
    if (e.response != null) { // This is the block that gets executed
      print('kmfovrnf');
      print(e.response!.data);
      print('=====');
      print(e.error);
      print('=====');
      print(e.response!.headers);
      print('=====');
      print(e.response!.requestOptions);
    } else {
      print('vinro');
      // Something happened in setting up or sending the request that triggered an Error
      print(e.requestOptions);
      print(e.message);
    }
    rethrow;
  } catch (e) {
    print('Network Helper catching error: $e');
    throw Exception(e);
  }

  print('Here');
  if (response.statusCode == 201) {
    final Map<String, dynamic> responseMap = response.data;

    print('Here22');
    return User.fromJson(responseMap);
  } else {
    print('Response : ${response.data}');
    throw Exception(response.data.toString());
  }
}

二、Dio调用终端日志 #

Performing hot restart...
Restarted application in 6,075ms.
I/flutter (28797): kmfovrnf
I/flutter (28797): <!DOCTYPE html>
<html lang="en">
<head>
  <meta http-equiv="content-type" content="text/html; charset=utf-8">
  <meta name="robots" content="NONE,NOARCHIVE">
  <title>DoesNotExist
          at /signup_person</title>
  <style type="text/css">
    html * { padding:0; margin:0; }
    body * { padding:10px 20px; }
    body * * { padding:0; }
    body { font:small sans-serif; background-color:#fff; color:#000; }
    body>div { border-bottom:1px solid #ddd; }
    h1 { font-weight:normal; }
    h2 { margin-bottom:.8em; }
    h3 { margin:1em 0 .5em 0; }
    h4 { margin:0 0 .5em 0; font-weight: normal; }
    code, pre { font-size: 100%; white-space: pre-wrap; word-break: break-word; }
    summary { cursor: pointer; }
    table { border:1px solid #ccc; border-collapse: collapse; width:100%; background:white; }
    tbody td, tbody th { vertical-align:top; padding:2px 3px; }
    thead th {
      padding:1px 6px 1px 3px; background:#fefefe; text-align:left;
      font-weight:normal; font-size:11px; border:1px solid #ddd;
=====
I/flutter (28797): Http status error [500]
=====
I/flutter (28797): keep-alive: timeout=5, max=100
I/flutter (28797): date: Wed, 04 Jan 2023 09:05:45 GMT
I/flutter (28797): transfer-encoding: chunked
I/flutter (28797): vary: Accept-Encoding
I/flutter (28797): content-encoding: gzip
I/flutter (28797): referrer-policy: same-origin
I/flutter (28797): content-type: text/html; charset=utf-8
I/flutter (28797): x-frame-options: DENY
I/flutter (28797): cross-origin-opener-policy: same-origin
I/flutter (28797): x-content-type-options: nosniff
I/flutter (28797): x-turbo-charged-by: LiteSpeed
I/flutter (28797): server: LiteSpeed
=====
I/flutter (28797): Instance of 'RequestOptions'
E/flutter (28797): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Exception: Error occurred
E/flutter (28797): #0      makeRequest (package:reprex/main.dart:84:7)
E/flutter (28797): <asynchronous suspension>
E/flutter (28797): #1      MyApp.build.<anonymous closure> (package:reprex/main.dart:25:21)
E/flutter (28797): <asynchronous suspension>
E/flutter (28797):

三、Postman测试结果 #

Postman中使用相同参数调用该接口，能正常返回201状态码。

四、切换http库后的代码及日志 #

http库实现代码 #

Uri url = Uri.https('XXXXXXX.XXXXX.com', '/signup_person');
var response = await http.post(
  url,
  body: {
    'email': email,
    'username': username,
    'password': password,
    'password2': password2
  },
);
print('=====================');
print('Response status: ${response.statusCode}');
print('=====================');
print('Response body: ${response.body}');
print('=====================');
print('Response request: ${response.request}');
print('=====================');

print('Request completed');

http库调用终端日志 #

I/flutter (30166): Response status: 500
I/flutter (30166): =====================
I/flutter (30166): Response body: <!DOCTYPE html>
<html lang="en">
<head>
  <meta http-equiv="content-type" content="text/html; charset=utf-8">
  <meta name="robots" content="NONE,NOARCHIVE">
  <title>SMTPRecipientsRefused
          at /signup_person</title>
  <style type="text/css">
    html * { padding:0; margin:0; }
    body * { padding:10px 20px; }
    body * * { padding:0; }
    body { font:small sans-serif; background-color:#fff; color:#000; }
    body>div { border-bottom:1px solid #ddd; }
    h1 { font-weight:normal; }
    h2 { margin-bottom:.8em; }
    h3 { margin:1em 0 .5em 0; }
    h4 { margin:0 0 .5em 0; font-weight: normal; }
    code, pre { font-size: 100%; white-space: pre-wrap; word-break: break-word; }
    summary { cursor: pointer; }
    table { border:1px solid #ccc; border-collapse: collapse; width:100%; background:white; }
    tbody td, tbody th { vertical-align:top; padding:2px 3px; }
    thead th {
      padding:1px 6px 1px 3px; background:#fefefe; text-align:left;
      font-weight:normal; font-size:11px
I/flutter (30166): =====================
I/flutter (30166): Response request: POST https://XXXXXX.XXX/signup_person
I/flutter (30166): =====================
I/flutter (30166): Request completed

排查思路 #

1. 后端后续操作失败：日志中出现DoesNotExist和SMTPRecipientsRefused错误，说明后端在成功创建用户后，执行后续操作（比如发送验证邮件、查找关联资源）时出错，导致返回500状态码，但用户数据已写入数据库。
2. 请求差异问题：Postman请求正常但Flutter端报错，需对比两者的请求头（比如Content-Type、User-Agent）是否一致。Dio默认发送application/json格式数据，若后端期望form-data或x-www-form-urlencoded，可能导致后续逻辑异常。
3. 邮箱有效性问题：SMTPRecipientsRefused表明SMTP服务器拒绝收件人，需检查测试用邮箱是否有效，是否被服务器列入黑名单。
4. 后端日志排查：查看后端完整错误日志，确认500错误的具体触发点，区分是资源不存在还是邮件发送失败导致的问题。

内容的提问来源于stack exchange，提问作者Olumide