天之奥特龙玩具视频:求助tomcat中发布jsp问题?

我做了个小项目，工具用jbuilder9，jdk是j2sdk1.4.2_11。数据库是mysql，tomcat是jbuilder自带。在我的机子上用jbuilder运行没问题。我把网页在tomcat5.0上发布就有问题了，无法登陆，500错误。郁闷了好几天都不知何原因，请高手指点一下，谢谢大家

url：String url="jdbc:mysql://localhost:3306/compbase?user=***&password=***";

网页部分代码：

<%@ page import="com.tmjt.ren.server.javabean.*"%>
<%@ page import="com.tmjt.ren.server.operation.*"%>
String user=request.getParameter("userName");

String pass=request.getParameter("userPass");

if(user!=null && !user.equals("")&&pass!=null&&!pass.equals(""))

{ if(user==null) user="";

if(pass==null) pass="";

User u=new User();

UserBean ub=new UserBean();

u.setUserName(user);

u.setUserPass(pass);

boolean x=ub.getLogin(u);

if(x) {

if(u.getUserName().equals("admin"))

{ response.sendRedirect("/client/admin/compQuery.jsp"); }

else { session.setAttribute("uname",user);

response.sendRedirect("/client/company/server.jsp"); }

错误信息：

HTTP Status 500 -

--------------------------------------------------------------------------------

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.service(JspServletWrapper.java:373)
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)

root cause

java.lang.NullPointerException
com.tmjt.ren.server.operation.UserBean.getLogin(UserBean.java:20)
org.apache.jsp.login_jsp._jspService(org.apache.jsp.login_jsp:70)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:99)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:325)
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/5.5.8 logs