背景:
golang的http服务,读取文件,提供给client下载时候。
出现 multiple http.writeHeader calls 错误。
func DownloadFile(w http.ResponseWriter, r *http.Request, sequence uint64, userid string) { userkey := userid filename := r.FormValue("filename") if len(userkey) <= 0 || len(filename) <= 0 { //........ } fp := fmt.Sprintf("%s%s/%s", g_sc.Rootdir, userkey, filename) fd, err := os.Open(fp) if err == nil { defer fd.Close() buf, err := ioutil.ReadAll(fd) if err != nil { //......... } else { size := len(buf) w.Header().Add("Content-Length", fmt.Sprintf("%d", size)) fmt.Fprint(w, string(buf)) } } }
问题出现在这几行代码:
size := len(buf)
w.Header().Add("Content-Length", fmt.Sprintf("%d", size))
fmt.Fprint(w, string(buf))
可以做如下修改:
buf := new(bytes.Buffer) buf.Write(...) if err { // you can use http.Error here, no response has been written yet http.Error(w, err.String, http.StatusInternalServerError) return } if err := buf.WriteTo(w); err != nil { log.Printf("WriteTo: %v", err) // you can not use http.Error here anymore. So just log the message (e.g. "broken pipe...") }
或者注释这两行代码
//size := len(buf)
//w.Header().Add("Content-Length", fmt.Sprintf("%d", size))
fmt.Fprint(w, string(buf))
//w.Header().Add("Content-Length", fmt.Sprintf("%d", size))
fmt.Fprint(w, string(buf))
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