Golang如何处理文件上传与下载 讲解multipart表单与静态文件服务

func uploadFile(w http.ResponseWriter, r *http.Request) {
    r.ParseMultipartForm(10 << 20) // 10MB limit

    file, handler, err := r.FormFile("myFile")
    if err != nil {
        fmt.Println("Error Retrieving the File")
        fmt.Println(err)
        return
    }
    defer file.Close()

    // 文件类型检查 (非常重要)
    contentType := handler.Header.Get("Content-Type")
    if contentType != "image/jpeg" && contentType != "image/png" {
        fmt.Println("Invalid file type")
        return
    }

    // 文件大小限制 (非常重要)
    if handler.Size > 5*1024*1024 { // 5MB
        fmt.Println("File too large")
        return
    }

    // 生成唯一文件名
    newFilename := uuid.New().String() + filepath.Ext(handler.Filename)

    f, err := os.OpenFile("./uploads/"+newFilename, os.O_WRONLY|os.O_CREATE, 0666)
    if err != nil {
        fmt.Println(err)
        return
    }
    defer f.Close()
    io.Copy(f, file)
    fmt.Fprintf(w, "Successfully Uploaded File\n")
}

func serveFiles(w http.ResponseWriter, r *http.Request) {
    fs := http.FileServer(http.Dir("static"))
    fs.ServeHTTP(w, r)
}

func main() {
    http.HandleFunc("/static/", serveFiles)
    log.Fatal(http.ListenAndServe(":8080", nil))
}

func downloadFile(w http.ResponseWriter, r *http.Request) {
    filePath := "./static/large_file.zip"
    http.ServeFile(w, r, filePath) // 简化版本，不带断点续传

    // 更完善的版本 (支持断点续传)
    // http.ServeContent(w, r, "large_file.zip", time.Now(), file)
}