我正在尝试使用go从我的计算机上传图片到一个网站。通常，我使用一个bash脚本将文件和密钥发送到服务器：
curl -F "image"=@"IMAGEFILE" -F "key"="KEY" URL
功能正常，但我正在尝试将此请求转换为我的golang程序。
http://matt.aimonetti.net/posts/2013/07/01/golang-multipart-file-upload-example/
我尝试过这个链接和其他许多链接，但是每次尝试的代码，服务器的响应都是“未发送图像”，而我不知道为什么。如果有人知道上面例子里发生了什么，请告诉我。
这里是一些示例代码。
简而言之，您需要使用mime/multipart包来构建表单。
package main
import (
"bytes"
"fmt"
"io"
"mime/multipart"
"net/http"
"net/http/httptest"
"net/http/httputil"
"os"
"strings"
)
func main() {
var client *http.Client
var remoteURL string
{
//setup a mocked http client.
ts := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
b, err := httputil.DumpRequest(r, true)
if err != nil {
panic(err)
}
fmt.Printf("%s", b)
}))
defer ts.Close()
client = ts.Client()
remoteURL = ts.URL
}
//prepare the reader instances to encode
values := map[string]io.Reader{
"file": mustOpen("main.go"), // lets assume its this file
"other": strings.NewReader("hello world!"),
}
err := Upload(client, remoteURL, values)
if err != nil {
panic(err)
}
}
func Upload(client *http.Client, url string, values map[string]io.Reader) (err error) {
// Prepare a form that you will submit to that URL.
var b bytes.Buffer
w := multipart.NewWriter(&b)
for key, r := range values {
var fw io.Writer
if x, ok := r.(io.Closer); ok {
defer x.Close()
}
// Add an image file
if x, ok := r.(*os.File); ok {
if fw, err = w.CreateFormFile(key, x.Name()); err != nil {
return
}
} else {
// Add other fields
if fw, err = w.CreateFormField(key); err != nil {
return
}
}
if _, err = io.Copy(fw, r); err != nil {
return err
}
}
// Don't forget to close the multipart writer.
// If you don't close it, your request will be missing the terminating boundary.
w.Close()
// Now that you have a form, you can submit it to your handler.
req, err := http.NewRequest("POST", url, &b)
if err != nil {
return
}
// Don't forget to set the content type, this will contain the boundary.
req.Header.Set("Content-Type", w.FormDataContentType())
// Submit the request
res, err := client.Do(req)
if err != nil {
return
}
// Check the response
if res.StatusCode != http.StatusOK {
err = fmt.Errorf("bad status: %s", res.Status)
}
return
}
func mustOpen(f string) *os.File {
r, err := os.Open(f)
if err != nil {
panic(err)
}
return r
}
form-data; name="data"; filename="%s", fn)
partHeader.Add("Content-Disposition", disp)
partHeader.Add("Content-Type", "image/jpeg")
part, err := writer.CreatePart(partHeader)
</pre> - Zhichang Yufile.Name() 不起作用之外，其他都很好。似乎它返回的是传递给 os.Open() 的文件路径而不是名称... (string) (len=37) "./internal/file_example_JPG_500kB.jpg" // Name 返回打开时文件的名称。 func (f *File) Name() string { return f.name } 如果我在 w.CreateFormFile() 中硬编码文件名，它就可以正常工作。谢谢 Attila - Lukas LukacmustOpen() 中打开了文件，但没有关闭它。你应该在完成后使用 defer file.Close() 关闭文件吗？ - lion_bash这是我使用的一个函数，它使用 io.Pipe() 来避免将整个文件读入内存或需要管理任何缓冲区。它仅处理单个文件，但可以通过在 goroutine 中添加更多部分轻松扩展以处理更多文件。正常情况下效果很好。错误路径还没有进行充分测试。
import (
"fmt"
"io"
"mime/multipart"
"net/http"
"os"
)
func UploadMultipartFile(client *http.Client, uri, key, path string) (*http.Response, error) {
body, writer := io.Pipe()
req, err := http.NewRequest(http.MethodPost, uri, body)
if err != nil {
return nil, err
}
mwriter := multipart.NewWriter(writer)
req.Header.Add("Content-Type", mwriter.FormDataContentType())
errchan := make(chan error)
go func() {
defer close(errchan)
defer writer.Close()
defer mwriter.Close()
w, err := mwriter.CreateFormFile(key, path)
if err != nil {
errchan <- err
return
}
in, err := os.Open(path)
if err != nil {
errchan <- err
return
}
defer in.Close()
if written, err := io.Copy(w, in); err != nil {
errchan <- fmt.Errorf("error copying %s (%d bytes written): %v", path, written, err)
return
}
if err := mwriter.Close(); err != nil {
errchan <- err
return
}
}()
resp, err := client.Do(req)
merr := <-errchan
if err != nil || merr != nil {
return resp, fmt.Errorf("http error: %v, multipart error: %v", err, merr)
}
return resp, nil
}
以下是适用于文件或字符串的选项：
package main
import (
"bytes"
"io"
"mime/multipart"
"os"
"strings"
)
func createForm(form map[string]string) (string, io.Reader, error) {
body := new(bytes.Buffer)
mp := multipart.NewWriter(body)
defer mp.Close()
for key, val := range form {
if strings.HasPrefix(val, "@") {
val = val[1:]
file, err := os.Open(val)
if err != nil { return "", nil, err }
defer file.Close()
part, err := mp.CreateFormFile(key, val)
if err != nil { return "", nil, err }
io.Copy(part, file)
} else {
mp.WriteField(key, val)
}
}
return mp.FormDataContentType(), body, nil
}
示例：
package main
import "net/http"
func main() {
form := map[string]string{"image": "@IMAGEFILE", "key": "KEY"}
ct, body, err := createForm(form)
if err != nil {
panic(err)
}
http.Post("https://stackoverflow.com", ct, body)
}
在我的单元测试中，为了使用这个问题的接受答案，我最终得到了以下重构代码：
func createMultipartFormData(t *testing.T, fieldName, fileName string) (bytes.Buffer, *multipart.Writer) {
var b bytes.Buffer
var err error
w := multipart.NewWriter(&b)
var fw io.Writer
file := mustOpen(fileName)
if fw, err = w.CreateFormFile(fieldName, file.Name()); err != nil {
t.Errorf("Error creating writer: %v", err)
}
if _, err = io.Copy(fw, file); err != nil {
t.Errorf("Error with io.Copy: %v", err)
}
w.Close()
return b, w
}
func mustOpen(f string) *os.File {
r, err := os.Open(f)
if err != nil {
pwd, _ := os.Getwd()
fmt.Println("PWD: ", pwd)
panic(err)
}
return r
}
b, w := createMultipartFormData(t, "image","../luke.png")
req, err := http.NewRequest("POST", url, &b)
if err != nil {
return
}
// Don't forget to set the content type, this will contain the boundary.
req.Header.Set("Content-Type", w.FormDataContentType())
func UploadFile(network, uri string, f multipart.File, h *multipart.FileHeader) error {
buf := new(bytes.Buffer)
writer := multipart.NewWriter(buf)
part, err := writer.CreateFormFile("file", h.Filename)
if err != nil {
log.Println(err)
return err
}
b, err := ioutil.ReadAll(f)
if err != nil {
log.Println(err)
return err
}
part.Write(b)
writer.Close()
req, _ := http.NewRequest("POST", uri, buf)
req.Header.Add("Content-Type", writer.FormDataContentType())
client := &http.Client{}
resp, err := client.Do(req)
if err != nil {
return err
}
defer resp.Body.Close()
b, _ = ioutil.ReadAll(resp.Body)
if resp.StatusCode >= 400 {
return errors.New(string(b))
}
return nil
}
为了扩展@attila-o的答案，这是我使用的Go代码来执行POST HTTP请求：
Curl表示：
curl -X POST \
http://localhost:9091/storage/add \
-H 'content-type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW' \
-F owner=0xc916Cfe5c83dD4FC3c3B0Bf2ec2d4e401782875e \
-F password=$PWD \
-F file=@./internal/file_example_JPG_500kB.jpg
前进方式：
client := &http.Client{
Timeout: time.Second * 10,
}
req, err := createStoragePostReq(cfg)
res, err := executeStoragePostReq(client, req)
func createStoragePostReq(cfg Config) (*http.Request, error) {
extraFields := map[string]string{
"owner": "0xc916cfe5c83dd4fc3c3b0bf2ec2d4e401782875e",
"password": "pwd",
}
url := fmt.Sprintf("http://localhost:%d%s", cfg.HttpServerConfig().Port(), lethstorage.AddRoute)
b, w, err := createMultipartFormData("file","./internal/file_example_JPG_500kB.jpg", "file_example_JPG_500kB.jpg", extraFields)
if err != nil {
return nil, err
}
req, err := http.NewRequest("POST", url, &b)
if err != nil {
return nil, err
}
req.Header.Set("Content-Type", w.FormDataContentType())
return req, nil
}
func executeStoragePostReq(client *http.Client, req *http.Request) (lethstorage.AddRes, error) {
var addRes lethstorage.AddRes
res, err := client.Do(req)
if err != nil {
return addRes, err
}
defer res.Body.Close()
data, err := ioutil.ReadAll(res.Body)
if err != nil {
return addRes, err
}
err = json.Unmarshal(data, &addRes)
if err != nil {
return addRes, err
}
return addRes, nil
}
func createMultipartFormData(fileFieldName, filePath string, fileName string, extraFormFields map[string]string) (b bytes.Buffer, w *multipart.Writer, err error) {
w = multipart.NewWriter(&b)
var fw io.Writer
file, err := os.Open(filePath)
if fw, err = w.CreateFormFile(fileFieldName, fileName); err != nil {
return
}
if _, err = io.Copy(fw, file); err != nil {
return
}
for k, v := range extraFormFields {
w.WriteField(k, v)
}
w.Close()
return
}
我发现这个教程对于澄清Go中文件上传的困惑非常有帮助。
基本上，你可以通过客户端使用form-data来上传文件，然后在服务器上使用以下简短的Go代码：
file, handler, err := r.FormFile("img") // img is the key of the form-data
if err != nil {
fmt.Println(err)
return
}
defer file.Close()
fmt.Println("File is good")
fmt.Println(handler.Filename)
fmt.Println()
fmt.Println(handler.Header)
f, err := os.OpenFile(handler.Filename, os.O_WRONLY|os.O_CREATE, 0666)
if err != nil {
fmt.Println(err)
return
}
defer f.Close()
io.Copy(f, file)
这里的r是*http.Request。 P.S. 这只是将文件存储在同一文件夹中，不执行任何安全检查。