MultipartFile.fromBytes request returns 'Required request part 'data' is not present' in Flutter Web

user_18425709 0
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so im currently new on flutter web and im trying to send a file to an API that accepts a file as an input. I've tried to use MultipartRequest for it, but the api always give response of "Required request part 'data' is not present". Here is the code of the api hit :

var postUri = Uri.parse("myApiUrl");
http.MultipartRequest request = new http.MultipartRequest("POST", postUri);
request.files.add(await http.MultipartFile.fromBytes("data", image));
http.StreamedResponse response = await request.send();

and this is the "image" byte (yes, it's a blank image):

[255, 216, 255, 224, 0, 16, 74, 70, 73, 70, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 255, 226, 2, 40, 73, 67, 67, 95, 80, 82, 79, 70, 73, 76, 69, 0, 1, 1, 0, 0, 2, 24, 0, 0, 0, 0, 2, 16, 0, 0, 109, 110, 116, 114, 82, 71, 66, 32, 88, 89, 90, 32, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 97, 99, 115, 112, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 246, 214, 0, 1, 0, 0, 0, 0, 211, 45, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9, 100, 101, 115, 99, 0, 0, 0, 240, 0, 0, 0, 116, 114, 88, 89, 90, 0, 0, 1, 100, 0, 0, 0, 20, 103, 88, 89, 90, 0, 0, 1, 120, 0, 0, 0, 20, 98, 88, 89, 90, 0, 0, 1, 140, 0, 0, 0, 20, 114, 84, 82, 67, 0, 0, 1, 160, 0, 0, 0, 40, 103, 84, 82, 67, 0, 0, 1, 160, 0, 0, 0, 40, 98, 84, 82, 67, 0, 0, 1, 160, 0, 0, 0, 40, 119, 116, 112, 116, 0, 0, 1, 200, 0, 0, 0, 20, 99, 112, 114, 116, 0, 0, 1, 220, 0, 0, 0, 60, 109, 108, 117, 99, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 12, 101, 110, 85, 83, 0, 0, 0, 88, 0, 0, 0, 28, 0, 115, 0, 82, 0, 71, 0, 66, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 88, 89, 90, 32, 0, 0, 0, 0, 0, 0, 111, 162, 0, 0, 56, 245, 0, 0, 3, 144, 88, 89, 90, 32, 0, 0, 0, 0, 0, 0, 98, 153, 0, 0, 183, 133, 0, 0, 24, 218, 88, 89, 90, 32, 0, 0, 0, 0, 0, 0, 36, 160, 0, 0, 15, 132, 0, 0, 182, 207, 112, 97, 114, 97, 0, 0, 0, 0, 0, 4, 0, 0, 0, 2, 102, 102, 0, 0, 242, 167, 0, 0, 13, 89, 0, 0, 19, 208, 0, 0, 10, 91, 0, 0, 0, 0, 0, 0, 0, 0, 88, 89, 90, 32, 0, 0, 0, 0, 0, 0, 246, 214, 0, 1, 0, 0, 0, 0, 211, 45, 109, 108, 117, 99, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 12, 101, 110, 85, 83, 0, 0, 0, 32, 0, 0, 0, 28, 0, 71, 0, 111, 0, 111, 0, 103, 0, 108, 0, 101, 0, 32, 0, 73, 0, 110, 0, 99, 0, 46, 0, 32, 0, 50, 0, 48, 0, 49, 0, 54, 255, 219, 0, 67, 0, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 3, 3, 3, 3, 4, 6, 4, 4, 4, 4, 4, 8, 6, 6, 5, 6, 9, 8, 10, 10, 9, 8, 9, 9, 10, 12, 15, 12, 10, 11, 14, 11, 9, 9, 13, 17, 13, 14, 15, 16, 16, 17, 16, 10, 12, 18, 19, 18, 16, 19, 15, 16, 16, 16, 255, 219, 0, 67, 1, 3, 3, 3, 4, 3, 4, 8, 4, 4, 8, 16, 11, 9, 11, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 255, 192, 0, 17, 8, 1, 224, 2, 208, 3, 1, 34, 0, 2, 17, 1, 3, 17, 1, 255, 196, 0, 21, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9, 255, 196, 0, 23, 16, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 17, 49, 255, 196, 0, 20, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 255, 196, 0, 22, 17, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 17, 33, 255, 218, 0, 12, 3, 1, 0, 2, 17, 3, 17, 0, 63, 0, 157, 64, 27, 104, 0, 6, 211, 111, 0, 40, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 63, 255, 217]

but everytime i run the request, the api always gives me error code 400 and tell me that the data is not present, i've tried to google it but they always say to use fromPath which is not supported in flutter web.

flutter-web api
2 Answers

I faced a similar issue while uploading files (any type) in FlutterWeb using file_picker: ^4.6.1 . I found this Github Issue which mentions the same error. The solution is to include a file name along with the MultiPartFile.

request.files.add(http.MultipartFile.fromBytes(
  "your_parameter_name",
  file,
  filename: "your_file_name",
));
user_132798800

you can pick your image using this code (image_picker 0.8.4+11 package is required)

 final XFile? pickedImageFile = await ImagePicker().pickImage(
    source: isCamera ? ImageSource.camera : ImageSource.gallery,
    imageQuality: imageQuality,
    maxWidth: maxWidth,
    preferredCameraDevice: CameraDevice.rear);

and upload it using this code (I upload to S3 bucket). It works fine for both Web and Android

@override
Future<String> uploadImage(XFile image) async {
final s3Key = Uri.https('[your code]', '[your code]');
try {
  final url = await http.get(s3Key, headers: {
"Content-type": "application/json",
'Authorization': 'Bearer $authToken'
};);
  final extractedData = json.decode(url.body) as Map<String, dynamic>;
  final String urlPath = extractedData['url'];
  final Response response = await http.put(Uri.parse(urlPath),
      body: await image.readAsBytes(),
      headers: {'Content-Type': 'image/jpeg'});
  if (response.statusCode == 200 || response.statusCode == 201) {
    final String responseData = urlPath.split('?')[0];
    return responseData;
  } else {
    return '';
  }
} catch (e) {
  rethrow;
}

}

user_133576460
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