


How to develop a simple file download function using MySQL and Go language
How to use MySQL and Go language to develop a simple file download function
Overview:
The file download function is one of the common requirements of many web applications. This article will introduce how to use MySQL and Go language to develop a simple and reliable file download function. We will use MySQL to store file-related metadata, such as file name, path, and size, and the Go language will be used to handle file download requests and provide download services.
Steps:
- Database design
First, we need to design a database to store the metadata of the file. We can create a table named "files" with the following fields: - id: the unique identifier of the file, you can use a self-increasing integer or UUID as the primary key.
- name: File name, stored in VARCHAR or TEXT type.
- path: File storage path, stored in VARCHAR or TEXT type.
- size: File size, stored using integer type.
You can use the following SQL statement to create a table:
CREATE TABLE files (
id INT AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(255),
path VARCHAR(255 ),
size INT
);
- File upload
In a web application, users can upload files to the server through the upload file form. Here we use the net/http library of Go language to handle file upload requests. The following is a sample code to handle a file upload request:
func uploadHandler(w http.ResponseWriter, r *http.Request) { file, handler, err := r.FormFile("file") if err != nil { // 处理错误 http.Error(w, err.Error(), http.StatusInternalServerError) return } defer file.Close() // 保存文件到服务器 path := "/path/to/save/files/" + handler.Filename f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE, 0666) if err != nil { // 处理错误 http.Error(w, err.Error(), http.StatusInternalServerError) return } defer f.Close() io.Copy(f, file) // 将文件元数据插入数据库 size := handler.Size name := handler.Filename insertSQL := "INSERT INTO files (name, path, size) VALUES (?, ?, ?)" _, err = db.Exec(insertSQL, name, path, size) if err != nil { // 处理错误 http.Error(w, err.Error(), http.StatusInternalServerError) return } fmt.Fprintf(w, "文件上传成功") }
- File Download
Now, we can implement the file download function. The user downloads the file by sending a GET request. We need to find the relevant information of the file based on the file's id and send the file content to the user.
The following is a sample code to handle a file download request:
func downloadHandler(w http.ResponseWriter, r *http.Request) { id := r.URL.Query().Get("id") // 根据文件id查询文件元数据 querySQL := "SELECT name, path, size FROM files WHERE id = ?" var name, path string var size int64 err := db.QueryRow(querySQL, id).Scan(&name, &path, &size) if err != nil { // 处理错误 http.Error(w, err.Error(), http.StatusInternalServerError) return } // 打开文件 file, err := os.Open(path) if err != nil { // 处理错误 http.Error(w, err.Error(), http.StatusInternalServerError) return } defer file.Close() // 设置响应头 w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=%s", name)) w.Header().Set("Content-Type", "application/octet-stream") w.Header().Set("Content-Length", fmt.Sprintf("%d", size)) // 发送文件数据给用户 io.Copy(w, file) }
- Start the Web server
Finally, we need to write a simple main function to start the Web server and Listen for file upload and download requests.
func main() { // 连接MySQL数据库 db, err := sql.Open("mysql", "user:password@tcp(localhost:3306)/database") if err != nil { log.Fatal(err) } defer db.Close() // 注册路由处理函数 http.HandleFunc("/upload", uploadHandler) http.HandleFunc("/download", downloadHandler) // 启动HTTP服务器 log.Fatal(http.ListenAndServe(":8080", nil)) }
To sum up, we use MySQL to store file metadata, and use Go language to process file upload and download requests, implementing a simple file download function. The above code examples provide a basic framework that you can modify and extend appropriately according to actual needs. I hope this article will help you develop a file download function!
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