1.使用以下sql语句创建一个log表 CREATE TABLE `cskaoyan_log` ( `id` int(11) NOT NULL AUTO_INCREMENT, `operation` varchar(255) DEFAULT NULL, `ip` varchar(255) DEFAULT NULL, `add_time` datetime DEFAULT NULL, `success` tinyint(1) DEFAULT NULL, `err_msg` varchar(255) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8mb4; 需要大家创建与之对应的实体类CskaoyanLog，提供的对应的成员变量 2.提供一个默认的Servlet，该默认的Servlet实现以下功能，当别人访问了一个你其他Servlet没有对应的请求的时候，记录下来 操作（URI）、客户端IP、访问时间 这些信息，然后将这个信息记录到上面的cskaoyan_log表中，需要大家更新：id、operation、ip、add_time这些字段，其余字段不需要更新

以下是对应的实体类`CskaoyanLog`：

public class CskaoyanLog {
    private int id;
    private String operation;
    private String ip;
    private Date addTime;
    private Boolean success;
    private String errMsg;

    // getter and setter methods
}

以下是默认的`Servlet`实现：

public class DefaultServlet extends HttpServlet {
    private static final Logger logger = LoggerFactory.getLogger(DefaultServlet.class);

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 记录请求信息到日志表中
        CskaoyanLog log = new CskaoyanLog();
        log.setOperation(request.getRequestURI());
        log.setIp(request.getRemoteAddr());
        log.setAddTime(new Date());
        log.setSuccess(false);
        log.setErrMsg("No corresponding servlet found");
        insertLog(log);

        // 返回404错误
        response.sendError(HttpServletResponse.SC_NOT_FOUND);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    private void insertLog(CskaoyanLog log) {
        // 插入日志记录到数据库
        Connection conn = null;
        PreparedStatement pstmt = null;
        try {
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/cskaoyan", "root", "123456");
            String sql = "INSERT INTO cskaoyan_log (operation, ip, add_time, success, err_msg) VALUES (?, ?, ?, ?, ?)";
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, log.getOperation());
            pstmt.setString(2, log.getIp());
            pstmt.setTimestamp(3, new Timestamp(log.getAddTime().getTime()));
            pstmt.setBoolean(4, log.getSuccess());
            pstmt.setString(5, log.getErrMsg());
            pstmt.executeUpdate();
        } catch (SQLException e) {
            logger.error("Error inserting log record: {}", e.getMessage());
        } finally {
            if (pstmt != null) {
                try {
                    pstmt.close();
                } catch (SQLException e) {
                    logger.error("Error closing PreparedStatement: {}", e.getMessage());
                }
            }
            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException e) {
                    logger.error("Error closing Connection: {}", e.getMessage());
                }
            }
        }
    }
}

该`Servlet`会在收到所有未被其他`Servlet`处理的请求时被调用，记录请求信息到日志表中，并返回404错误。其中，`insertLog()`方法用于将日志记录插入到数据库中。