go 文件上传下载代码

https://blog.csdn.net/xmcy001122/article/details/104654096/

package main

import (
   "fmt"
   "io"
   "net/http"
   "net/url"
   "os"
   "strconv"
   "strings"
)

func upload(w http.ResponseWriter, req *http.Request) {
contentType := req.Header.Get("content-type")
contentLen := req.ContentLength

   fmt.Printf("upload content-type:%s,content-length:%d", contentType, contentLen)
   if !strings.Contains(contentType, "multipart/form-data") {
       w.Write([]byte("content-type must be multipart/form-data"))
       return
   }
   if contentLen >= 4*1024*1024 { // 10 MB
       w.Write([]byte("file to large,limit 4MB"))
       return
   }

   err := req.ParseMultipartForm(4 * 1024 * 1024)
   if err != nil {
       //http.Error(w, err.Error(), http.StatusInternalServerError)
       w.Write([]byte("ParseMultipartForm error:" + err.Error()))
       return
   }

   if len(req.MultipartForm.File) == 0 {
       w.Write([]byte("not have any file"))
       return
   }

for name, files := range req.MultipartForm.File {
fmt.Printf("req.MultipartForm.File,name=%s", name)

       if len(files) != 1 {
           w.Write([]byte("too many files"))
           return
       }
       if name == "" {
           w.Write([]byte("is not FileData"))
           return
       }

       for _, f := range files {
           handle, err := f.Open()
           if err != nil {
               w.Write([]byte(fmt.Sprintf("unknown error,fileName=%s,fileSize=%d,err:%s", f.Filename, f.Size, err.Error())))
               return
           }

           path := "./" + f.Filename
           dst, _ := os.Create(path)
           io.Copy(dst, handle)
           dst.Close()
           fmt.Printf("successful uploaded,fileName=%s,fileSize=%.2f MB,savePath=%s \n", f.Filename, float64(contentLen)/1024/1024, path)

           w.Write([]byte("successful,url=" + url.QueryEscape(f.Filename)))
       }
   }
}

func getContentType(fileName string) (extension, contentType string) {
arr := strings.Split(fileName, ".")

   // see: https://tool.oschina.net/commons/
   if len(arr) >= 2 {
       extension = arr[len(arr)-1]
       switch extension {
       case "jpeg", "jpe", "jpg":
           contentType = "image/jpeg"
       case "png":
           contentType = "image/png"
       case "gif":
           contentType = "image/gif"
       case "mp4":
           contentType = "video/mpeg4"
       case "mp3":
           contentType = "audio/mp3"
       case "wav":
           contentType = "audio/wav"
       case "pdf":
           contentType = "application/pdf"
       case "doc", "":
           contentType = "application/msword"
       }
   }
   // .*（二进制流，不知道下载文件类型）
   contentType = "application/octet-stream"
   return
}

func download(w http.ResponseWriter, req *http.Request) {
   if req.RequestURI == "/favicon.ico" {
       return
   }

fmt.Printf("download url=%s \n", req.RequestURI)

   filename := req.RequestURI[1:]
   enEscapeUrl, err := url.QueryUnescape(filename)
   if err != nil {
       w.Write([]byte(err.Error()))
       return
   }

   f, err := os.Open("./" + enEscapeUrl)
   if err != nil {
       w.Write([]byte(err.Error()))
       return
   }

   info, err := f.Stat()
   if err != nil {
       w.Write([]byte(err.Error()))
       return
   }

   _, contentType := getContentType(filename)
   w.Header().Set("Content-Disposition", "attachment; filename="+filename)
   //w.Header().Set("Content-Type", http.DetectContentType(fileHeader))
   w.Header().Set("Content-Type", contentType)
   w.Header().Set("Content-Length", strconv.FormatInt(info.Size(), 10))

f.Seek(0, 0)
io.Copy(w, f)
}

func main() {
   fmt.Printf("linsten on :8080 \n")
   http.HandleFunc("/file/upload", upload)
   http.HandleFunc("/", download)
   http.ListenAndServe(":8080", nil)
}

go 文件上传下载代码

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