Passing file from JavaScript to Go server

Question

I am trying to pass a set of FORM values from client to server. FORM values include files, user names and other details as well.

how do i decode the file in the server side. Here i Use go lang as my server. i have created a model in my golang so that i can decode the value passed during server call.

type Details {

    PhotographValue         os.File `json:"photographvalue"`
    AdharValue          os.File `json:"adharvalue"`
    userName        string `json:"username"`
}

//Decoding part

var clientValues Details
decoder := json.NewDecoder(req.Body)
err := decoder.Decode(&clientValues)

In clientValues i get string data. but the file data is nil. How can i achieve this?

PS : i am not using the usual file upload method as i have other details too also, i am manipulating those details in javascript before passing on to server.

Answer 1

If you pass your files as a part of multipart form you should parse it as form and use later as a separate jsons.

func handleForm(w http.ResponseWriter, req *http.Request) {
    const maxAllowedSizeInBytes = 512 * 1024
    err := req.ParseMultipartForm(maxAllowedSizeInBytes)
    if err != nil {
        // handle error here
        w.WriteHeader(http.StatusBadRequest)
        return
    }

    photographValue, _, err := req.FormFile("photographvalue")
    if err != nil {
        // handle error here
        w.WriteHeader(http.StatusBadRequest)
        return
    }
    adharValue, _, err := req.FormFile("adharvalue")
    if err != nil {
        // handle error here
        w.WriteHeader(http.StatusBadRequest)
        return
    }

    // photograph := struct{...} {}
    // json.NewDecoder(file).Decode(&photograph)
    // or write it to file
    username := req.FormValue("username")
    ....
}

photographValue and adharValue conform io.Reader and you can use it to read your json file or write it to file in the system.