multipart writer example with json

main.go

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"mime"
	"mime/multipart"
	"mime/quotedprintable"
	"net/http"
	"net/textproto"
	"strings"
)

var quoteEscaper = strings.NewReplacer("\\", "\\\\", `"`, "\\\"")

func escapeQuotes(s string) string {
	return quoteEscaper.Replace(s)
}

func writeJSON(w *multipart.Writer, name string, v interface{}) error {
	header := textproto.MIMEHeader{}
	header.Add("Content-Disposition", fmt.Sprintf("form-data; name=\"%s\"", escapeQuotes(name)))
	header.Add("Content-Type", mime.FormatMediaType("application/json", map[string]string{"charset": "UTF-8"}))
	header.Add("Content-Transfer-Encoding", "quoted-printable")
	pw, err := w.CreatePart(header)
	if err != nil {
		return err
	}
	qpw := quotedprintable.NewWriter(pw)
	encoder := json.NewEncoder(qpw)
	return encoder.Encode(v)
}

func main() {
	b := &bytes.Buffer{}
	writer := multipart.NewWriter(b)
	writeJSON(writer, "xx", map[string]string{
		"한글키": "값",
	})
	ww, _ := writer.CreateFormFile("yy", "a.jpg")
	ww.Write([]byte{1, 2, 3})
	writer.Close()
	fmt.Println(string(b.Bytes()))

	req, _ := http.NewRequest("GET", "localhost", b)
	req.Header.Set("Content-Type", writer.FormDataContentType())
	req.ParseMultipartForm(1 << 10)
	f := req.MultipartForm.File["yy"]
	fmt.Println(f)
	fmt.Println(req.PostFormValue("xx"))

	// r := multipart.NewReader(b, writer.Boundary())
	// p, _ := r.NextPart()
	// fmt.Println(p.FormName())
	// decoder := json.NewDecoder(p)

	// var body interface{}
	// decoder.Decode(&body)
	// fmt.Println(body)
}