golang文件上傳

1.上傳文件主要三步處理：

表單中增加enctype="multipart/form-data"
服務端調用r.ParseMultipartForm,把上傳的文件存儲在內存和臨時文件中
使用r.FormFile獲取文件句柄，然后對文件進行存儲等處理。

// 示例代碼
r.ParseMultipartForm(32 << 20)
file, handler, err := r.FormFile("uploadfile")
defer file.Close()
f, err := os.OpenFile("./test/"+handler.Filename, os.O_WRONLY|os.O_CREATE, 0666) 
defer f.Close()
io.Copy(f, file)

2.客戶端上傳文件

package main

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)

	//關鍵的一步操作
	fileWriter, err := bodyWriter.CreateFormFile("uploadfile", filename)
	if err != nil {
		fmt.Println("error writing to buffer")
		return err
	}

	//打開文件句柄操作
	fh, err := os.Open(filename)
	if err != nil {
		fmt.Println("error opening file")
		return err
	}
	defer fh.Close()
	
	//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)
}

3.服務端處理上傳文件

http.HandleFunc("/upload", upload)

// 處理/upload 邏輯
func upload(w http.ResponseWriter, r *http.Request) {
	fmt.Println("method:", r.Method) //獲取請求的方法
	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)  // 此處假設當前目錄下已存在test目錄
		if err != nil {
			fmt.Println(err)
			return
		}
		defer f.Close()
		io.Copy(f, file)
	}
}