编写一个使用QueryRunner类和ResultSetHandler接口，对数据库数据增删改查的代码

以下是一个使用QueryRunner类和ResultSetHandler接口，对数据库数据增删改查的示例代码：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.ResultSetHandler;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

public class DBUtilsExample {

    private static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    private static final String DB_URL = "jdbc:mysql://localhost:3306/test";
    private static final String USER = "root";
    private static final String PASS = "password";

    public static void main(String[] args) throws SQLException, ClassNotFoundException {
        // 加载驱动
        Class.forName(JDBC_DRIVER);

        // 建立连接
        Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);

        // 创建QueryRunner对象
        QueryRunner qr = new QueryRunner();

        // 插入数据
        String insertSql = "INSERT INTO user(name, age) VALUES (?, ?)";
        qr.update(conn, insertSql, "张三", 20);

        // 删除数据
        String deleteSql = "DELETE FROM user WHERE id=?";
        qr.update(conn, deleteSql, 1);

        // 更新数据
        String updateSql = "UPDATE user SET age=? WHERE name=?";
        qr.update(conn, updateSql, 25, "张三");

        // 查询单条数据
        String queryOneSql = "SELECT * FROM user WHERE name=?";
        ResultSetHandler<User> userHandler = new BeanHandler<>(User.class);
        User user = qr.query(conn, queryOneSql, userHandler, "张三");
        System.out.println(user.getName() + ", " + user.getAge());

        // 查询多条数据
        String queryListSql = "SELECT * FROM user";
        ResultSetHandler<List<User>> userListHandler = new BeanListHandler<>(User.class);
        List<User> userList = qr.query(conn, queryListSql, userListHandler);
        for (User u : userList) {
            System.out.println(u.getName() + ", " + u.getAge());
        }

        // 查询数据总数
        String countSql = "SELECT COUNT(*) FROM user";
        ResultSetHandler<Long> countHandler = new ScalarHandler<>();
        Long count = qr.query(conn, countSql, countHandler);
        System.out.println("数据总数：" + count);

        // 关闭连接
        conn.close();
    }
}

在这个示例代码中，我们使用QueryRunner类和ResultSetHandler接口完成了数据库的增删改查操作。其中，BeanHandler和BeanListHandler是用来将查询结果映射成Java对象的ResultSetHandler实现类，ScalarHandler则是用来获取单个值的ResultSetHandler实现类。通过使用这些实现类，我们可以更加方便地操作数据库。