关于javabean的问题

我的环境是windowsxp+jdk1.5_03+Tomcat5.59
在IE里调用javaBean的过程中,发生了如下错误,
type Exception report
message 
description The server encountered an internal error () that prevented it from fulfilling this request.
exception 
org.apache.jasper.JasperException: /javaBean.jsp(5,0) The value for the useBean class attribute Box is invalid.
org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:39)
org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:405)
org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:146)
org.apache.jasper.compiler.Generator$GenerateVisitor.visit(Generator.java:1223)
org.apache.jasper.compiler.Node$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:3270)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:189)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:286)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:267)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:255)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:556)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:293)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.9 logs.jsp源码:
<%@ page contentType="text/html;charset=GB2312"%>
<%@ page import="b.Box" %>
<html>
<body>
<jsp:useBean id="box" class="Box" scope="page">
</jsp:useBean>
<% box.setLength(10);
box.setWidth(11);
box.setHeight(12);
out.println("在jsp中使用javaBean<br>");
out.println(box.getLength());
%>
</body>
</html>
javaBean的代码:
package b;
public class Box{
double length;
double width;
double height;
public Box()
{
length=0;
width=0;
height=0;
}
public void setLength(double length)
{
this.length=length;
}
public void setHeight(double height)
{
this.height=height;
}
public void setWidth(double width)
{
this.width=width;
}
public double getLength()
{
return length;
}
public double getHeight()
{
return height;
}
public double getWidth()
{
return width;
}
}
我将Box.class文件放在了WEB-INF\classes\b目录下了
请各位指教,不胜感激!