如何在java中通过数据库更改xml属性值

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

public class UpdateXMLAttribute {
    public static void main(String[] args) {
        // 连接到数据库
        Connection connection = null;
        try {
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "username", "password");
            
            // 读取XML文件并解析
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            DocumentBuilder builder = factory.newDocumentBuilder();
            Document document = builder.parse("path/to/xml/file.xml");
            
            // 定位到需要更改的XML属性
            XPath xPath = XPathFactory.newInstance().newXPath();
            String expression = "//element[@attribute='oldValue']";
            Node node = (Node) xPath.compile(expression).evaluate(document, XPathConstants.NODE);
            
            if (node != null && node.getNodeType() == Node.ELEMENT_NODE) {
                Element element = (Element) node;
                
                // 更新XML属性值
                element.setAttribute("attribute", "newValue");
                
                // 将更新后的XML数据写回到XML文件
                TransformerFactory transformerFactory = TransformerFactory.newInstance();
                Transformer transformer = transformerFactory.newTransformer();
                DOMSource source = new DOMSource(document);
                StreamResult result = new StreamResult(new File("path/to/xml/file.xml"));
                transformer.transform(source, result);
                
                // 更新数据库中的数据
                String sql = "UPDATE mytable SET xml_data = ? WHERE id = ?";
                PreparedStatement statement = connection.prepareStatement(sql);
                statement.setString(1, documentToString(document));
                statement.setInt(2, 1); // 假设需要更新的数据在数据库中的ID为1
                statement.executeUpdate();
                
                System.out.println("XML属性值已成功更改并更新到数据库和XML文件中。");
            } else {
                System.out.println("未找到需要更改的XML属性。");
            }
        } catch (SQLException | ParserConfigurationException | SAXException | IOException | XPathExpressionException | TransformerException e) {
            e.printStackTrace();
        } finally {
            // 关闭数据库连接
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    
    // 将Document对象转换为字符串
    private static String documentToString(Document document) throws TransformerException {
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Transformer transformer = transformerFactory.newTransformer();
        StringWriter writer = new StringWriter();
        transformer.transform(new DOMSource(document), new StreamResult(writer));
        return writer.getBuffer().toString();
    }
}