使用 multer 将带有 flutter 的 multipartrequest 发送到 Nodejs 服务器时，req.file 在 NodeJS 中未定义

Question

我在构建一个应用程序来将图像从带有 multipartrequest 的 flutter 应用程序上传到带有 nodejs 和 multer 的服务器时遇到问题。

这是我的代码和错误消息：

颤动：

print("TEST1");
                      var request =
                          http.MultipartRequest("POST", Uri.parse(url));
                      print("TEST2");
                      request.fields['request'] =
                          jsonEncode(<String, int>{'todoId': todoId});
                      print("TEST3");
                      try {
                        File file =
                            await File.fromRawPath(result.files.single.bytes!);
                        print("TEST4");
                        http.MultipartFile file_forrequest =http.MultipartFile('filetoupload',
                            file.readAsBytes().asStream(), file.lengthSync(),
                            filename: file.path.split("/").last);
                        request.files.add(file_forrequest);
                      } catch (e) {
                        print("ERROR: " + e.toString());
                      }
                      print("TEST5");
                      request.headers.addAll(<String, String>{
                        "Authorization": "Bearer " + token.toString(),
                        "Content-Type": "application/json"
                      });
                      print("TEST6");
                      var response = await request.send();
                      print("TEST7");
                      print(response.statusCode);
                      String res = await response.stream.bytesToString();
                      print(res);

nodejs代码：

app.post(`${vorPath}/otherFileToToDo`, jsonParser, berechtigungmitgruppepruefen, uploadFileToDo("filetoupload"), async (req, res) => {
    console.log("FILES:");
    console.log(req.files);
    console.log("__");
    const request = JSON.parse(req.body.request);
    const todoId = request.todoId;
    const peopleId = req.user.peopleId;
    const filePath = req.file.path;
    try {
        const todos = await prisma.todos.findMany({
            where: {
                id: todoId,
                zustaendige: {
                    some: {
                        peopleId: peopleId
                    }
                }
            }
        });
        if (todos.length == 1) {
            const todo = todos[0];
            const otherFilesPaths = todo.otherFilesPaths;
            otherFilesPaths.push(filePath);
            await prisma.todos.update({
                where: {
                    id: todoId
                },
                data: {
                    otherFilesPaths: otherFilesPaths
                }
            })
            res.sendStatus(200);
        } else {
            const todos_2 = await prisma.todos.findMany({
                where: {
                    id: todoId
                }
            })
            if (todos_2.length == 1) {
                res.sendStatus(401);
            } else {
                res.sendStatus(404);
            }
        }
    } catch (error) {
        console.log("ERROR: " + error);
        res.sendStatus(500);
    }
    res.sendStatus(200);
})

这里是使用的函数uploadFileToDo的代码：

function uploadFileToDo(file) {
    const storage = multer.diskStorage({
        destination: (req, file, cb) => {
            cb(null, '/mnt/sknasserver/todofiles/');
        },
        filename: (req, file, cb) => {
            const withoutLastFour = file.originalname.slice(0, -4);
            const lastFour = file.originalname.slice(-4);
            const newFileName = withoutLastFour + "-" + password_generator.generate({
                length: 10,
                symbols: false,
                numbers: true
            }) + lastFour;
            cb(null, newFileName);
        },
    });
    const upload = multer({ storage: storage });
    const uploadsingle = upload.single(file);
    return (req, res, next) => {
        uploadsingle(req, res, (err) => {
            if (err) {
                console.error('Error during file upload:', err);
                return res.status(400).send('Error during file upload: ' + err.message);
            }
            console.log('File uploaded successfully:', req.file);
            req.file.path = "/todofiles/" + req.file.filename;
            next();
        });
    };

}

服务器控制台的输出：

file
App listening on port 5000
null
File uploaded successfully: undefined
/home/schemannkurier/api/sk_backend/api.js:108
            req.file.path = "/todofiles/" + req.file.filename;
                                                     ^

TypeError: Cannot read properties of undefined (reading 'filename')
    at /home/schemannkurier/api/sk_backend/api.js:108:54
    at done (/home/schemannkurier/api/sk_backend/node_modules/multer/lib/make-middleware.js:45:7)
    at indicateDone (/home/schemannkurier/api/sk_backend/node_modules/multer/lib/make-middleware.js:49:68)
    at Multipart.<anonymous> (/home/schemannkurier/api/sk_backend/node_modules/multer/lib/make-middleware.js:166:7)
    at Multipart.emit (node:events:514:28)
    at Multipart.emit (node:domain:488:12)
    at emitCloseNT (node:internal/streams/destroy:132:10)
    at process.processTicksAndRejections (node:internal/process/task_queues:81:21)

Node.js v20.10.0

flutter 调试控制台中的输出：

TEST1
TEST2
TEST3
TEST4
ERROR: Unsupported operation: _Namespace
TEST5
TEST6
TEST7
502
<html>
<head><title>502 Bad Gateway</title></head>
<body>
<center><h1>502 Bad Gateway</h1></center>
<hr><center>nginx/1.25.5</center>
</body>
</html>
6
<!-- a padding to disable MSIE and Chrome friendly error page -->

顺便说一句，在邮递员中，路线可以使用该参数：

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请帮助我，我尝试了一切......

Answer 1

您的问题解决了吗，在这里面临同样的问题。经过多次调试，现在我得到了期望 image 的其他字段。当尝试使用 req.file 访问文件字段时，未定义。我认为图像没有从 flutter 端上传到服务器。有人帮忙 使用 Dio/Http 包从 Flutter 向 Express Server 发送视频文件和表单数据的问题，Android 手机附加调试模式