java从数据库下载文件

import java.io.*;
import java.sql.*;

public class FileDownloader {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/mydatabase";
        String user = "username";
        String password = "password";
        String query = "SELECT file_data FROM files WHERE file_id = ?";

        try (Connection conn = DriverManager.getConnection(url, user, password);
             PreparedStatement pstmt = conn.prepareStatement(query)) {

            pstmt.setInt(1, 1); // 假设我们要下载的文件ID为1
            ResultSet rs = pstmt.executeQuery();

            if (rs.next()) {
                Blob blob = rs.getBlob("file_data");
                InputStream inputStream = blob.getBinaryStream();
                FileOutputStream outputStream = new FileOutputStream("downloaded_file.jpg");

                byte[] buffer = new byte[4096];
                int bytesRead;
                while ((bytesRead = inputStream.read(buffer)) != -1) {
                    outputStream.write(buffer, 0, bytesRead);
                }

                outputStream.close();
                inputStream.close();
                System.out.println("文件下载成功！");
            } else {
                System.out.println("未找到文件！");
            }
        } catch (SQLException | IOException e) {
            e.printStackTrace();
        }
    }
}