在实现JavaBean处理用户登陆的时候发出的问题

Question

Exception reportmessage /dologin.jsp (line: 4, column: 0) The value for the useBean class attribute com.lo.User is invalid.The value for the useBean class attribute com.lo.User is invalid.这个是什么意思？以下是dologin前四行。包名类名检查均无错<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%>   <%@ page import="com.dao.*,com.lo.*" %><jsp:useBean id="loginUser" class="com.lo.User" scope="page"/>