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使用dio发送的请求体为Uint8List格式时，转换器将Uint8List转化为String的问题。 #371

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使用dio发送的请求体为Uint8List格式时，转换器将Uint8List转化为String的问题。#371
@jianzi0307

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@jianzi0307
jianzi0307
opened on Jul 9, 2019 · edited by jianzi0307

最近做的一个项目用到protobuf，使用dio发送的post请求数据为Uint8List格式：

UserMeRequest req = UserMeRequest.create();
req.token = await Storage.getToken();
Uint8List reqBuffer = req.writeToBuffer();
Uint8List responseBuffer = await dio.post('user/me', data: reqBuffer);  // <------
UserMeResponse resp = UserMeResponse.fromBuffer(responseBuffer);
print('$resp <<<<<<<<<<<<<<userMe');

服务端总提示protobuf数据格式不正确，跟踪代码我发现dio转换器总是返回String格式：
DefaultTransformer 返回的数据将data转化为String类型。

Future<String> transformRequest(RequestOptions options) async {
    var data = options.data ?? "";
    if (data is! String) {
      if (options.contentType.mimeType == ContentType.json.mimeType) {
        return json.encode(options.data);
      } else if (data is Map) {
        return Transformer.urlEncodeMap(data);
      }
    }
    return data.toString();  /// <=================== 调用了data.toString()方法
  }

这样会导致服务端处理的时候将接收的字节数组按照字符串处理，导致格式无法识别。

建议：
能否添加Uint8List格式的判断，不做处理直接返回data，

像这样：

Future<dynamic> transformRequest(RequestOptions options) async {
    var data = options.data ?? "";
    if (data is! String) {
      if (options.contentType.mimeType == ContentType.json.mimeType) {
        return json.encode(options.data);
      } else if (data is Map) {
        return Transformer.urlEncodeMap(data);
      } else if (data is Uint8List) {  /// <========= 添加Uint8List格式判断条件
        return data;
      }
    }
    return data.toString();  
  }

Activity

jianzi0307

jianzi0307 commented on Jul 9, 2019

@jianzi0307
jianzi0307
on Jul 9, 2019 · edited by jianzi0307
Author
class Uint8ListTransformer extends DefaultTransformer {
  @override
  Future<String> transformRequest(RequestOptions options) async {
    if (options.data is Uint8List) {
      return String.fromCharCodes(options.data);
    } else {
      return super.transformRequest(options);
    }
  }
}

BaseOptions options = BaseOptions(
   baseUrl: "https://xxxx.com/",
   ......
   requestEncoder: (String request, RequestOptions options) {
        Uint8List list = Uint8List.fromList(request.codeUnits);
        return list;
    },
);
Dio dio = Dio(options);
dio.transformer = Uint8ListTransformer();
......
jianzi0307
closed this as completedon Jul 9, 2019
AlexV525
mentioned this on Sep 29, 2019
nextwhale

nextwhale commented on Nov 14, 2020

@nextwhale
nextwhale
on Nov 14, 2020 · edited by nextwhale

You can create a method to transform proto buffer to Stream like this:

    dynamic transformPbMessage2Steam(GeneratedMessage pbMessage) {
        List<int> buffer = pbMessage.writeToBuffer();
        return Stream.fromIterable([buffer]);
    }

The usage example:

    var model = HelloRequest();
    model.id = '100288273';
    model.name = '我住隔壁我姓王';
    
    var res = await Dio().post('/', data: transformPbMessage2Steam(model));
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          使用dio发送的请求体为Uint8List格式时，转换器将Uint8List转化为String的问题。 · Issue #371 · cfug/dio