如何用java从MySql数据库中检索Blob pdf文件

import java.io.FileOutputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class RetrieveBlobPDF {
    public static void main(String[] args) {
        String jdbcUrl = "jdbc:mysql://localhost:3306/mydatabase";
        String username = "root";
        String password = "password";
        
        try {
            // 建立数据库连接
            Connection connection = DriverManager.getConnection(jdbcUrl, username, password);
            
            // SQL查询语句
            String sql = "SELECT pdf_data FROM pdf_table WHERE pdf_id = ?";
            
            // 创建PreparedStatement对象
            PreparedStatement statement = connection.prepareStatement(sql);
            statement.setInt(1, 1); // 设置查询参数
            
            // 执行查询
            ResultSet resultSet = statement.executeQuery();
            
            if (resultSet.next()) {
                // 获取Blob对象
                InputStream inputStream = resultSet.getBlob("pdf_data").getBinaryStream();
                
                // 创建文件输出流
                FileOutputStream outputStream = new FileOutputStream("output.pdf");
                
                // 读取输入流并写入输出流
                byte[] buffer = new byte[1024];
                int length;
                while ((length = inputStream.read(buffer)) != -1) {
                    outputStream.write(buffer, 0, length);
                }
                
                // 关闭流
                inputStream.close();
                outputStream.close();
                
                System.out.println("PDF文件已成功检索并保存。");
            } else {
                System.out.println("未找到PDF文件。");
            }
            
            // 关闭数据库连接
            connection.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}