springboot项目 java写一个工具类，查找出mysql数据库中其中一个库的所有表和字段和字段长度并生成一个xml文件

可以使用JDBC连接MySQL数据库获取数据库元数据信息，然后使用Java的XML生成库将元数据转换成XML文件。以下是实现代码的示例：

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamWriter;

public class DBMetadataToXMLTool {
    public static void main(String[] args) throws IOException, SQLException, XMLStreamException {
        String jdbcUrl = "jdbc:mysql://localhost:3306/mydb";
        String jdbcUser = "username";
        String jdbcPassword = "password";
        String xmlFilePath = "/path/to/xmlfile.xml";

        Connection conn = null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            conn = DriverManager.getConnection(jdbcUrl, jdbcUser, jdbcPassword);

            DatabaseMetaData metadata = conn.getMetaData();
            ResultSet tables = metadata.getTables(null, null, null, new String[] {"TABLE"});

            List<String> tableNames = new ArrayList<>();
            while (tables.next()) {
                tableNames.add(tables.getString("TABLE_NAME"));
            }

            XMLOutputFactory factory = XMLOutputFactory.newInstance();
            XMLStreamWriter writer = factory.createXMLStreamWriter(new FileWriter(new File(xmlFilePath)));

            writer.writeStartDocument();
            writer.writeStartElement("database");

            for (String tableName: tableNames) {
                ResultSet columns = metadata.getColumns(null, null, tableName, null);
                writer.writeStartElement("table");
                writer.writeAttribute("name", tableName);

                while (columns.next()) {
                    String columnName = columns.getString("COLUMN_NAME");
                    String dataType = columns.getString("TYPE_NAME");
                    int columnSize = columns.getInt("COLUMN_SIZE");
                    
                    writer.writeStartElement("column");
                    writer.writeAttribute("name", columnName);
                    writer.writeAttribute("type", dataType);
                    writer.writeAttribute("size", String.valueOf(columnSize));
                    writer.writeEndElement(); // column
                }

                writer.writeEndElement(); // table
            }

            writer.writeEndElement(); // database
            writer.writeEndDocument();
            writer.flush();
            writer.close();

        } catch (ClassNotFoundException | SQLException | IOException | XMLStreamException e) {
            e.printStackTrace();
        } finally {
            if (conn != null) {
                conn.close();
            }
        }
    }
}