我在学习用jboss,tomcat 搭建ejb服务时，报以下异常，请问这代表什么意思呀！！

谢谢各位了！！

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HTTP Status 500 -

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type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:510)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)

root cause

java.lang.ClassCastException
com.sun.corba.se.impl.javax.rmi.PortableRemoteObject.narrow(PortableRemoteObject.java:229)
javax.rmi.PortableRemoteObject.narrow(PortableRemoteObject.java:137)
org.apache.jsp.common_jsp.jspInit(common_jsp.java:28)
org.apache.jasper.runtime.HttpJspBase.init(HttpJspBase.java:78)
org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:155)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:315)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)

note The full stack trace of the root cause is available in the Apache Tomcat/5.5.17 logs.

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Apache Tomcat/5.5.17

出错页程序：

<%@ page import="mypack.*"%>
<%@ page import="java.util.Properties"%>
<%@ page errorPage="errorpage.jsp"%>
<%@ page import="javax.ejb.*"%>
<%@ page import="javax.naming.*"%>
<%@ page import="javax.rmi.PortableRemoteObject"%>
<%@ page import="java.rmi.RemoteException"%>

<%

private BookDBEJB bookDB;

public void jspInit(){

bookDB = (BookDBEJB)getServletContext.getAttribute("bookDB");

if(bookDB==null){

try{

InitialContext ic = new InitialContext();
Object objRef=ic.lookup("java:comp/env/ejb/BookDBEJB");
BookDBEJBHome home=(BookDBEJBHome)PortableRemoteObject.narrow(objRef,mypack.BookDBEJBHome.class);
bookDB=home.create();
getServletContext().setAttribute("bookDB",bookDB);

}catch(RemoteException ex){

System.out.println("Could not create database bean."+ex.getMessage());
}catch(CreateException ex){

System.out.println("Could not create database bean."+ex.getMessage());
}catch(NamingException ex){

System.out.println("Unable to look up home:"+"java:comp/env/ejb/BookDBEJB"+ex.getMessage());
}
}
}

public void jspDestroy(){

bookDB=null;

}

public String convert(String s){

try{

return new String(s.getBytes("ISO-8859-1"),"GB2312");

}catch(Exception e){

return null;

}

}

%>

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谢谢！！！！！