如何在 Dart http 库中使用 StreamedRequest 上传文件？

Question

我想通过这样的非multipart/form-data 请求上传文件：

POST http://127.0.0.1/upload
Cache-Control: no-cache

< /path/to/file/in/disk

（我进行了测试，它成功地将文件从 JetBrain Rider 的 REST 客户端上传到了我的 REST 端点。）

http 包中有一个StreamedRequest 类，但我没有找到任何构造函数或设置器来插入字节流或文件内容。

如何使用StreamedRequest 在 Dart 中上传文件？

Answer 1

我只是要发布 phqb 的解决方案，以防 pastebin 链接失效：

final file = new File(filePath);

final streamedRequest =
    new http.StreamedRequest('POST', Configurations.getUserContentsApiUri('/upload'))
      ..headers.addAll({
        'Cache-Control': 'no-cache',
        'Authorization': 'Bearer $uploadToken',
      });
streamedRequest.contentLength = await file.length();
file.openRead().listen((chunk) {
  print(chunk.length);
  streamedRequest.sink.add(chunk);
}, onDone: () {
  streamedRequest.sink.close();
});

await streamedRequest.send();
print('after response');

Answer 2

在我使用的一些旧代码中

  /// Send a POST request to the Docker service.
  Future<http.ByteStream> _streamRequestStream(
      String path, Stream<List<int>> stream,
      {Map<String, String> query}) async {
    assert(stream != null);
    final url = serverReference.buildUri(path, query);
    final request = new http.StreamedRequest('POST', url)
      ..headers.addAll(headersTar);
    stream.listen(request.sink.add);
    final http.BaseResponse response =
        await request.send().then(http.Response.fromStream);
    if (response.statusCode < 200 || response.statusCode >= 300) {
      throw new DockerRemoteApiError(
          response.statusCode, response.reasonPhrase, null);
    }
    return (response as http.StreamedResponse).stream;
  }

这可能会做你想做的事

https://github.com/bwu-dart/bwu_docker/blob/master/lib/src/remote_api.dart#L160-L178

它使用http 包

import 'package:http/http.dart' as http;

Answer 3

更新：

发布此消息一天后，我意识到这实际上并没有测量 上传 进度，而只是 读取 来自本地 JSON 有效负载的字节的进度，即几乎是瞬间的。如果/当我弄清楚如何实际衡量上传进度时，我会更新这个答案。

---

原答案：

这对我有用：

import 'dart:convert';
import 'package:http/http.dart' as http;

// ...

final jsonPayload = {'base64File': 'abc123', 'something': 'else'};

// We are using a StreamedRequest so we can track the upload progress
final streamedRequest = http.StreamedRequest("POST", apiUri);
streamedRequest.headers['content-type'] = 'application/json';

// Length transferred (to calculate upload progress)
var transferredLength = 0;
// Upload progress (from 0.0 to 1.0)
var uploadProgress = 0.0;
// The stringified JSON payload
var stringEncodedPayload = jsonEncode(jsonPayload);
// Total length (to calculate upload progress)
var totalLength = stringEncodedPayload.length;

// Create a stream of the payload string
Stream.value(stringEncodedPayload)
  // Transform the string-stream to a byte stream (List<int>)
  .transform(utf8.encoder)
  // Start reading the stream in chunks, submitting them to the streamedRequest for upload
  .listen((chunk) {
    transferredLength += chunk.length;
    uploadProgress = transferredLength / totalLength;
    print("Chunk: ${chunk.length}, transferred: $transferredLength, progress: $uploadProgress");
    streamedRequest.sink.add(chunk);
  }, onDone: () {
    print("Done. Total: $totalLength, transferred: $transferredLength, progress: $uploadProgress");
    streamedRequest.sink.close();
  });

final result = await client.send(streamedRequest).then(http.Response.fromStream);


print("----------->");
print(result.statusCode);
print(result.body);
print("<-----------");

输出：

flutter: Chunk: 1024, transferred: 1024, progress: 0.0008807503580198599
flutter: Chunk: 1024, transferred: 2048, progress: 0.0017615007160397197
flutter: Chunk: 1024, transferred: 3072, progress: 0.0026422510740595796
...
flutter: Chunk: 1024, transferred: 1159168, progress: 0.9970094052784814
flutter: Chunk: 1024, transferred: 1160192, progress: 0.9978901556365013
flutter: Chunk: 1024, transferred: 1161216, progress: 0.9987709059945211
flutter: Chunk: 1024, transferred: 1162240, progress: 0.9996516563525409
flutter: Chunk: 405, transferred: 1162645, progress: 1.0
flutter: Done. Total: 1162645, transferred: 1162645, progress: 1.0