我正在针对 Mapbox 编写一个 API 客户端,将一批 svg 图像上传到自定义 map 。他们为此提供的 api 记录在一个可以正常工作的示例 cUrl 调用中:curl -F images=@include/mapbox/sprites_dark/aubergine_selected.svg "https://api.mapbox.com/styles/v1/<my_company>/<my_style_id>/sprite?access_token=$MAPBOX_API_KEY" --trace-ascii /dev/stdout
当尝试从 golang 做同样的事情时,我很快发现 multiform 库非常有限,并编写了一些代码来发出类似于上面提到的 cUrl 请求的请求。
func createMultipartFormData(fileMap map[string]string) (bytes.Buffer, *multipart.Writer) {
var b bytes.Buffer
var err error
w := multipart.NewWriter(&b)
var fw io.Writer
for fileName, filePath := range fileMap {
h := make(textproto.MIMEHeader)
h.Set("Content-Disposition",
fmt.Sprintf(`form-data; name="%s"; filename="%s"`, "images", fileName))
h.Set("Content-Type", "image/svg+xml")
if fw, err = w.CreatePart(h); err != nil {
fmt.Printf("Error creating form File %v, %v", fileName, err)
continue
}
fileContents, err := ioutil.ReadFile(filePath)
fileContents = bytes.ReplaceAll(fileContents, []byte("\n"), []byte("."))
blockSize := 64
remainder := len(fileContents) % blockSize
iterations := (len(fileContents) - remainder) / blockSize
newBytes := []byte{}
for i := 0; i < iterations; i++ {
start := i * blockSize
end := i*blockSize + blockSize
newBytes = append(newBytes, fileContents[start:end]...)
newBytes = append(newBytes, []byte("\n")...)
}
if remainder > 0 {
newBytes = append(newBytes, fileContents[iterations*blockSize:]...)
newBytes = append(newBytes, []byte("\n")...)
}
if err != nil {
fmt.Printf("Error reading svg file: %v: %v", filePath, err)
continue
}
_, err = fw.Write(newBytes)
if err != nil {
log.Debugf("Could not write file to multipart: %v, %v", fileName, err)
continue
}
}
w.Close()
return b, w
}
除了在实际请求中设置 header : bytes, formWriter := createMultipartFormData(filesMap)
req, err := http.NewRequest("Post", fmt.Sprintf("https://api.mapbox.com/styles/v1/%v/%v/sprite?access_token=%v", "my_company", styleID, os.Getenv("MAPBOX_API_KEY")), &bytes)
if err != nil {
return err
}
req.Header.Set("User-Agent", "curl/7.64.1")
req.Header.Set("Accept", "*/*")
req.Header.Set("Content-Length", fmt.Sprintf("%v", len(bytes.Bytes())))
req.Header.Set("Content-Type", formWriter.FormDataContentType())
byts, _ := httputil.DumpRequest(req, true)
fmt.Println(string(byts))
res, err := http.DefaultClient.Do(req)
甚至想尽可能限制行长并复制 cUrl 使用的编码,但到目前为止还没有运气。有经验的人知道为什么这适用于 cUrl 而不是 golang?
最佳答案
好吧,我承认解决您的任务的“拼图”的所有部分都可以在网上找到,这有两个问题:
所以,这是一个可行的解决方案。
package main
import (
"bytes"
"fmt"
"io"
"io/ioutil"
"mime"
"mime/multipart"
"net/http"
"net/textproto"
"net/url"
"os"
"path/filepath"
"strconv"
"strings"
)
func main() {
const (
dst = "https://api.mapbox.com/styles/v1/AcmeInc/Style_001/sprite"
fname = "path/to/a/sprite/image.svg"
token = "an_invalid_token"
)
err := post(dst, fname, token)
if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(1)
}
}
func post(dst, fname, token string) error {
u, err := url.Parse(dst)
if err != nil {
return fmt.Errorf("failed to parse destination url: %w", err)
}
form, err := makeRequestBody(fname)
if err != nil {
return fmt.Errorf("failed to prepare request body: %w", err)
}
q := u.Query()
q.Set("access_token", token)
u.RawQuery = q.Encode()
hdr := make(http.Header)
hdr.Set("Content-Type", form.contentType)
req := http.Request{
Method: "POST",
URL: u,
Header: hdr,
Body: ioutil.NopCloser(form.body),
ContentLength: int64(form.contentLen),
}
resp, err := http.DefaultClient.Do(&req)
if err != nil {
return fmt.Errorf("failed to perform http request: %w", err)
}
defer resp.Body.Close()
_, _ = io.Copy(os.Stdout, resp.Body)
return nil
}
type form struct {
body *bytes.Buffer
contentType string
contentLen int
}
func makeRequestBody(fname string) (form, error) {
ct, err := getImageContentType(fname)
if err != nil {
return form{}, fmt.Errorf(
`failed to get content type for image file "%s": %w`,
fname, err)
}
fd, err := os.Open(fname)
if err != nil {
return form{}, fmt.Errorf("failed to open file to upload: %w", err)
}
defer fd.Close()
stat, err := fd.Stat()
if err != nil {
return form{}, fmt.Errorf("failed to query file info: %w", err)
}
hdr := make(textproto.MIMEHeader)
cd := mime.FormatMediaType("form-data", map[string]string{
"name": "images",
"filename": fname,
})
hdr.Set("Content-Disposition", cd)
hdr.Set("Contnt-Type", ct)
hdr.Set("Content-Length", strconv.FormatInt(stat.Size(), 10))
var buf bytes.Buffer
mw := multipart.NewWriter(&buf)
part, err := mw.CreatePart(hdr)
if err != nil {
return form{}, fmt.Errorf("failed to create new form part: %w", err)
}
n, err := io.Copy(part, fd)
if err != nil {
return form{}, fmt.Errorf("failed to write form part: %w", err)
}
if int64(n) != stat.Size() {
return form{}, fmt.Errorf("file size changed while writing: %s", fd.Name())
}
err = mw.Close()
if err != nil {
return form{}, fmt.Errorf("failed to prepare form: %w", err)
}
return form{
body: &buf,
contentType: mw.FormDataContentType(),
contentLen: buf.Len(),
}, nil
}
var imageContentTypes = map[string]string{
"png": "image/png",
"jpg": "image/jpeg",
"jpeg": "image/jpeg",
"svg": "image/svg+xml",
}
func getImageContentType(fname string) (string, error) {
ext := filepath.Ext(fname)
if ext == "" {
return "", fmt.Errorf("file name has no extension: %s", fname)
}
ext = strings.ToLower(ext[1:])
ct, found := imageContentTypes[ext]
if !found {
return "", fmt.Errorf("unknown file name extension: %s", ext)
}
return ct, nil
}
一些关于实现的随机注释可帮助您理解这些概念:bytes.Buffer
实例。它有一个很好的属性,指向它的指针(
*bytes.Buffer
)同时实现了 io.Writer
和 io.Reader
因此可以很容易地与处理 I/O 的 Go 标准库的其他部分组成。 关于Golang 多部分文件表单请求,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/63636454/