[求助]为什么错误？？

错误显示：
org.apache.jasper.JasperException: /checklogon.jsp(3,0) The value for the useBean class attribute cuug.BuyerBean is invalid.
org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:39)
org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:376)
org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:150)
org.apache.jasper.compiler.Generator$GenerateVisitor.visit(Generator.java:1217)
org.apache.jasper.compiler.Node$UseBean.accept(Node.java:1116)
org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2163)
org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2213)
org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2219)
org.apache.jasper.compiler.Node$Root.accept(Node.java:456)
org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2163)
org.apache.jasper.compiler.Generator.generate(Generator.java:3261)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:244)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:461)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:442)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:430)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:511)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:274)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:853)

//////////////////////////////////////////////////////////////////////
checklogon.jsp代码：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<%@ page language="java" contentType="text/html;charset=GB2312"%>
<jsp:useBean class="cuug.BuyerBean" id="buyer" scope="page"></jsp:useBean>
<HTML>
<HEAD>
<META name=”CHECKLOGON” >
<TITLE>
CUUG ON LINE BOOK STORE – MEMBER LOGIN
</TITLE>
</HEAD>
<BODY BGCOLOR="#FFFFFF">
<H1 align="center">CUUG 网上书店</H1>
<%
String memberID = request.getParameter("memberID");
String pwd = request.getParameter("pwd");
buyer.setMemberID(memberID);
buyer.setPwd(pwd);
%>
<% int logonTimes = buyer.getLogontimes() ;
if (logonTimes > 0){
session.putValue("memberID",memberID);
%>
<H2 align="center"><%= buyer.getMemberName() %>欢迎你第
<%= logonTimes +1%>次来到CUUG网上书店</H2>
<H2 align="center"><A href="booklist.jsp">进入书店</A></H2>
<%
}
else{
%>
<H2 align="center">对不起,<%= memberID %>你的用户名和密码不一致</H2>
<H2 align="center"><A href="default.htm">重新登录</A></H2>

<%
}
%>

</BODY>
</HTML>
/////////////////////////////////////////////////////////////////
BuyerBean.java代码：
package cuug;

import java.sql.*;
public class BuyerBean {

private String memberID = null ; //会员ID
private String memberName = null; //会员姓名
private String pwd = null; //密码
private int logontimes = -1; //登录的次数
private static String strDBDriver = "sun.jdbc.odbc.JdbcOdbcDriver"; //JDBC驱动
private static String strDBUrl = "jdbc:odbc:bookstore"; //数据源 ，
private Connection conn =null; //连接
private ResultSet rs = null; //结果集

public BuyerBean (){
//加载JDBC-ODBC驱动
try {
Class.forName(strDBDriver );
}
//捕获异常
catch(java.lang.ClassNotFoundException e){
System.err.println("BuyerBean():" + e.getMessage());
}
}

//获得登录次数，登录的会员的名字也在该方法调用时获得
public int getLogontimes(){
String strSql = null;
try{
conn = DriverManager.getConnection(strDBUrl);
Statement stmt = conn.createStatement();
strSql = "Select logonTimes,membername from buyerInfo where memberID = '" +
memberID + "' and pwd ='" + pwd + "'";
rs = stmt.executeQuery(strSql);
while (rs.next()){
// 登录的次数
logontimes = rs.getInt("logonTimes");
//会员姓名
memberName = rs.getString("membername");
}
rs.close();
//如果是合法会员则将其登录次数加1
if (logontimes != -1 ) {
strSql = "Update buyerInfo set logonTimes = logonTimes +1 where memberID ='" + memberID + "'";
stmt.executeUpdate(strSql);
}
stmt.close();
conn.close();

}
//捕获异常
catch(SQLException e){
System.err.println("BuyerBean.getLogontimes():" + e.getMessage());
}
return logontimes ;
}
//设置memberID属性；
public void setMemberID(String ID){
this.memberID = ID;
}
//设置pwd 属性
public void setPwd(String password){
this.pwd = password;
}
//获得该会员的真实姓名，必须在取该会员登录的次数之后才能被赋予正确的值
public String getMemberName(){
return memberName;
}
}