diff --git a/en/04.5.md b/en/04.5.md
index 25803e49..bbc62ef7 100644
--- a/en/04.5.md
+++ b/en/04.5.md
@@ -4,58 +4,67 @@ Suppose you have a website like Instagram and you want users to upload their bea
You have to add property `enctype` to the form that you want to use for uploading photos. There are three possible values for this property:
- application/x-www-form-urlencoded Transcode all characters before uploading (default).
- multipart/form-data No transcoding. You must use this value when your form has file upload controls.
- text/plain Convert spaces to "+", but no transcoding for special characters.
+```
+application/x-www-form-urlencoded Transcode all characters before uploading (default).
+multipart/form-data No transcoding. You must use this value when your form has file upload controls.
+text/plain Convert spaces to "+", but no transcoding for special characters.
+```
+
Therefore, the HTML content of a file upload form should look like this:
-
-
- Upload file
-
-
-
-
-
+```
+
+
+ Upload file
+
+
+
+
+
+```
+
We need to add a function on the server side to handle this form.
- http.HandleFunc("/upload", upload)
+```
+http.HandleFunc("/upload", upload)
- // upload logic
- 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))
+// upload logic
+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)
+ }
+}
+```
- 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)
- }
- }
As you can see, we need to call `r.ParseMultipartForm` for uploading files. The function `maxMemory` argument. After you call `ParseMultipartForm`, the file will be saved in the server memory with `maxMemory` size. If the file size is larger than `maxMemory`, the rest of the data will be saved in a system temporary file. You can use `r.FormFile` to get the file handle and use `io.Copy` to save to your file system.
@@ -69,11 +78,13 @@ We use three steps for uploading files as follows:
The file handler is the `multipart.FileHeader`. It uses the following struct:
- type FileHeader struct {
- Filename string
- Header textproto.MIMEHeader
- // contains filtered or unexported fields
- }
+```
+type FileHeader struct {
+ Filename string
+ Header textproto.MIMEHeader
+ // contains filtered or unexported fields
+}
+```
@@ -83,65 +94,68 @@ Figure 4.5 Print information on server after receiving file.
I showed an example of using a form to a upload a file. We can impersonate a client form to upload files in Go as well.
- package main
+```
+package main
- import (
- "bytes"
- "fmt"
- "io"
- "io/ioutil"
- "mime/multipart"
- "net/http"
- "os"
- )
+import (
+ "bytes"
+ "fmt"
+ "io"
+ "io/ioutil"
+ "mime/multipart"
+ "net/http"
+ "os"
+)
- func postFile(filename string, targetUrl string) error {
- bodyBuf := &bytes.Buffer{}
- bodyWriter := multipart.NewWriter(bodyBuf)
-
- // this step is very important
- fileWriter, err := bodyWriter.CreateFormFile("uploadfile", filename)
- if err != nil {
- fmt.Println("error writing to buffer")
- return err
- }
-
- // open file handle
- fh, err := os.Open(filename)
- if err != nil {
- fmt.Println("error opening file")
- return err
- }
-
- //iocopy
- _, err = io.Copy(fileWriter, fh)
- if err != nil {
- return err
- }
-
- contentType := bodyWriter.FormDataContentType()
- bodyWriter.Close()
-
- resp, err := http.Post(targetUrl, contentType, bodyBuf)
- if err != nil {
- return err
- }
- defer resp.Body.Close()
- resp_body, err := ioutil.ReadAll(resp.Body)
- if err != nil {
- return err
- }
- fmt.Println(resp.Status)
- fmt.Println(string(resp_body))
- return nil
- }
+func postFile(filename string, targetUrl string) error {
+ bodyBuf := &bytes.Buffer{}
+ bodyWriter := multipart.NewWriter(bodyBuf)
+
+ // this step is very important
+ fileWriter, err := bodyWriter.CreateFormFile("uploadfile", filename)
+ if err != nil {
+ fmt.Println("error writing to buffer")
+ return err
+ }
+
+ // open file handle
+ fh, err := os.Open(filename)
+ if err != nil {
+ fmt.Println("error opening file")
+ return err
+ }
+
+ //iocopy
+ _, err = io.Copy(fileWriter, fh)
+ if err != nil {
+ return err
+ }
+
+ contentType := bodyWriter.FormDataContentType()
+ bodyWriter.Close()
+
+ resp, err := http.Post(targetUrl, contentType, bodyBuf)
+ if err != nil {
+ return err
+ }
+ defer resp.Body.Close()
+ resp_body, err := ioutil.ReadAll(resp.Body)
+ if err != nil {
+ return err
+ }
+ fmt.Println(resp.Status)
+ fmt.Println(string(resp_body))
+ return nil
+}
+
+// sample usage
+func main() {
+ target_url := "http://localhost:9090/upload"
+ filename := "./astaxie.pdf"
+ postFile(filename, target_url)
+}
+```
- // sample usage
- func main() {
- target_url := "http://localhost:9090/upload"
- filename := "./astaxie.pdf"
- postFile(filename, target_url)
- }
The above example shows you how to use a client to upload files. It uses `multipart.Write` to write files into cache and sends them to the server through the POST method.