upload file
通过表单从浏览器上传文件到服务器
upload.gtpl
<html>
<head>
<title>上传文件</title>
</head>
<body>
<form enctype="multipart/form-data" action="/upload" method="post">
<input type="file" name="uploadfile" />
<input type="hidden" name="token" value=""/>
<input type="submit" value="upload" />
</form>
</body>
</html>
main.go
package main
import (
"crypto/md5"
"fmt"
"html/template"
"io"
"log"
"net/http"
"os"
"strconv"
"time"
)
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(handler.Filename, os.O_WRONLY|os.O_CREATE, 0666)
if err != nil {
fmt.Println(err)
return
}
defer f.Close()
io.Copy(f, file)
}
}
func login(w http.ResponseWriter, r *http.Request) {
fmt.Println("method:", r.Method) //获取请求的方法
if r.Method == "GET" {
t, _ := template.ParseFiles("login.gtpl")
log.Println(t.Execute(w, nil))
} else {
fmt.Println("username:", r.Form["username"])
fmt.Println("password:", r.Form["password"])
}
}
func main() {
http.HandleFunc("/login", login)
http.HandleFunc("/upload", upload)
log.Println("listening...")
http.ListenAndServe(":8890", nil)
}
处理文件上传我们需要调用 r.ParseMultipartForm,里面的参数表示 maxMemory,调用 ParseMultipartForm 之后,上传的文件存储在 maxMemory 大小的内存里面,如果文件大小超过了maxMemory,那么剩下的部分将存储在系统的临时文件中。我们可以通过 r.FormFile获取上面的文件句柄,然后实例中使用了 io.Copy 来存储文件
上传文件步骤分析
- 表单中增加 enctype=”multipart/form-data”
- 服务端调用 r.ParseMultipartForm,把上传的文件存储在内存和临时文件中
- 使用 r.FormFile 获取文件句柄,然后对文件进行存储等处理
客户端上传文件
package main
import (
"io"
"os"
"fmt"
"bytes"
"net/http"
"io/ioutil"
"mime/multipart"
)
func postFile(file_name string, target_url string) error {
bodyBuf := &bytes.Buffer{}
bodyWriter := multipart.NewWriter(bodyBuf)//create a writer object
//create a form
fileWriter, err := bodyWriter.CreateFormFile("uploadfile", file_name)
if err != nil {
fmt.Println("error writing to buffer")
return err
}
fh, err := os.Open(file_name)
if err != nil {
fmt.Println("error Opening file")
return err
}
defer fh.Close()
_, err = io.Copy(fileWriter, fh)
if err != nil {
return err
}
contentType := bodyWriter.FormDataContentType()
bodyWriter.Close()
resp, err := http.Post(target_url, 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 main() {
target_url := "http://localhost:8890/upload"
file_name := "test.pdf"
err := postFile(file_name, target_url)
if err != nil {
fmt.Println("upload filed!!!")
}
}
客户端通过 multipart.Write 把文件的文本流写入一个缓存中,然后调用 http 的 Post 方法把缓存传到服务器