Golang实现文件上传下载教程

• main.go # 主程序入口
• upload/ # 存放上传文件的目录

func init() {
    if _, err := os.Stat("upload"); os.IsNotExist(err) {
        os.Mkdir("upload", 0755)
    }
}

func handleUpload(w http.ResponseWriter, r *http.Request) {
    if r.Method != "POST" {
        http.Error(w, "仅支持 POST 请求", http.StatusMethodNotAllowed)
        return
    }
// 解析 multipart 表单，限制大小为 32MB
err := r.ParseMultipartForm(32 << 20)
if err != nil {
    http.Error(w, "解析表单失败", http.StatusBadRequest)
    return
}

file, handler, err := r.FormFile("file")
if err != nil {
    http.Error(w, "获取文件失败", http.StatusBadRequest)
    return
}
defer file.Close()

// 创建本地文件
dst, err := os.Create(filepath.Join("upload", handler.Filename))
if err != nil {
    http.Error(w, "创建文件失败", http.StatusInternalServerError)
    return
}
defer dst.Close()

// 拷贝文件内容
_, err = io.Copy(dst, file)
if err != nil {
    http.Error(w, "保存文件失败", http.StatusInternalServerError)
    return
}

fmt.Fprintf(w, "文件 %s 上传成功", handler.Filename)
}

  
  上传

func handleDownload(w http.ResponseWriter, r *http.Request) {
    filename := filepath.Base(r.URL.Path[len("/download/"):]) // 获取文件名
    filepath := filepath.Join("upload", filename)
// 检查文件是否存在
if _, err := os.Stat(filepath); os.IsNotExist(err) {
    http.NotFound(w, r)
    return
}

// 设置响应头
w.Header().Set("Content-Disposition", "attachment; filename="+filename)
w.Header().Set("Content-Type", "application/octet-stream")

// 发送文件
http.ServeFile(w, r, filepath)
}

func main() {
    http.HandleFunc("/upload", handleUpload)
    http.HandleFunc("/download/", handleDownload)
// 可选：提供一个上传页面
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
    if r.URL.Path != "/" {
        http.NotFound(w, r)
        return
    }
    html := `<h3>文件上传</h3><form ... >...</form>`
    fmt.Fprint(w, html)
})

fmt.Println("服务器启动，端口 :8080")
log.Fatal(http.ListenAndServe(":8080", nil))
}