I am using vaadin upload to upload files on web application with polymer. And I am using golang for back-end.

 vaadin-upload target=\"../upload\" max-files=\"20\" accept=\"application/pdf,image/*\" method=\"POST\" /vaadin-upload 

I checked that encoding type used in vaadin upload is multipart/form-data.My golang code is below.

func upload(w http.ResponseWriter, r *http.Request) { fmt.Println(\"method:\", r.Method) if r.Method == \"GET\" { crutime := time.Now().Unix() h := md5.New() io.WriteString(h, strconv.FormatInt(crutime, 10)) token := fmt.Sprintf(\"%x\", h.Sum(nil)) t, _ := template.ParseFiles(\"upload.gtpl\") t.Execute(w, token) } else { r.ParseMultipartForm(32 20) file, handler, err := r.FormFile(\"uploadFile\") if err != nil { fmt.Println(err) return defer file.Close() fmt.Fprintf(w, \"%v\", handler.Header) f, err := os.OpenFile(\"./test/\"+handler.Filename, os.O_WRONLY|os.O_CREATE, 0666) if err != nil { fmt.Println(err) return defer f.Close() io.Copy(f, file)

It gives error on server side http: no such file. I checked this error is returned by FormFile when the provided file field name is either not present in the request or not a file field.

How do I correct my form file name. Although everything seems fine on front-end

私信 访问主页

Answering my own question for those who are facing same problem. Found out some code which can access file without knowing the key value.

func UploadHandler(res http.ResponseWriter, req *http.Request) {  var (  status int  err error  defer func() {  if nil != err {  http.Error(res, err.Error(), status)  }()  // parse request  // const _24K = (1 20) * 24  if err = req.ParseMultipartForm(32 20); nil != err {  status = http.StatusInternalServerError  return  fmt.Println(\"No memory problem\") for _, fheaders := range req.MultipartForm.File {  for _, hdr := range fheaders {  // open uploaded  var infile multipart.File  if infile, err = hdr.Open(); nil != err {  status = http.StatusInternalServerError  return  // open destination  var outfile *os.File  if outfile, err = os.Create(\"./uploaded/\" + hdr.Filename); nil != err {  status = http.StatusInternalServerError  return  // 32K buffer copy  var written int64  if written, err = io.Copy(outfile, infile); nil != err {  status = http.StatusInternalServerError  return  res.Write([]byte(\"uploaded file:\" + hdr.Filename + \";length:\" + strconv.Itoa(int(written)))) 

私信 访问主页

Use exactly the same name for doing r.FormFile(\"selectedFile\") that is there in your HTML tag. The key is mapped to input name used in your frontend HTML tag.

Below is my implementation:

 file type=\"file\" name=\"selectedFile\"const ( S3_REGION = \"Your region\" S3_BUCKET = \"Your Bucket Name\"func uploadFile(w http.ResponseWriter, r *http.Request) { fmt.Fprintf(w, \"Uploading File\") r.ParseMultipartForm(32 20) file, handler, err := r.FormFile(\"selectedFile\") //  if err != nil { fmt.Println(\"Error Retrieving the File\") fmt.Println(err) return defer file.Close() fmt.Printf(\"Uploaded File: %+v\", handler.Filename) fmt.Printf(\"File Size: %+v\", handler.Size) fmt.Printf(\"MIME Header: %+v\", handler.Header) s, err := session.NewSession( aws.Config{Region: aws.String(S3_REGION)}) if err != nil { log.Fatal(err) var size int64 = handler.Size buffer := make([]byte, size) file.Read(buffer) _, err = s3.New(s).PutObject( s3.PutObjectInput{ Bucket: aws.String(S3_BUCKET), Key: aws.String(handler.Filename), ACL: aws.String(\"private\"), Body: bytes.NewReader(buffer), ContentLength: aws.Int64(size), ContentType: aws.String(http.DetectContentType(buffer)), ContentDisposition: aws.String(\"attachment\"), ServerSideEncryption: aws.String(\"AES256\"),

私信 访问主页

Did a quick test and it appears that the vaadin-upload uses file as the form data parameter name for the file. So in the line

file, handler, err := r.FormFile(\"uploadFile\")

replace uploadFile with file and it should work.

It is documented on the vaadin homepage that