org.apache.jasper.JasperException

My OS is Debian Linux. I am using TOMCAT5 with Kaffe VM. I want to install JAMM which is a java interface for virtual mail domains management. But it is not working. I try it many times but no way i cant understand the problem. Here is my Tomcat error report. Thanks to everone.
 
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.service (JspServletWrapper.java:372)
      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:802)
      java.lang.reflect.Method.invoke0 (Method.java)
      java.lang.reflect.Method.invoke (Method.java:255)
      org.apache.catalina.security.SecurityUtil$1.run (SecurityUtil.java:243)
      java.security.AccessController.doPrivileged (AccessController.java:195)
      javax.security.auth.Subject.doAsPrivileged (Subject.java:250)
      org.apache.catalina.security.SecurityUtil.execute (SecurityUtil.java:272)
      org.apache.catalina.security.SecurityUtil.doAsPrivilege (SecurityUtil.java:161)


root cause

java.lang.NullPointerException
      org.apache.struts.util.RequestUtils.computeURL (RequestUtils.java:521)
      org.apache.struts.util.RequestUtils.computeURL (RequestUtils.java:436)
      org.apache.struts.util.RequestUtils.computeURL (RequestUtils.java:396)
      org.apache.struts.taglib.logic.RedirectTag.doEndTag (RedirectTag.java:294)
      org.apache.jsp.index_jsp._jspx_meth_logic_redirect_0 (index_jsp.java:146)
      org.apache.jsp.index_jsp._jspService (index_jsp.java:82)
      org.apache.jasper.runtime.HttpJspBase.service (HttpJspBase.java:94)
      javax.servlet.http.HttpServlet.service (HttpServlet.java:802)
      org.apache.jasper.servlet.JspServletWrapper.service (JspServletWrapper.java:324)
      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:802)
      java.lang.reflect.Method.invoke0 (Method.java)
      java.lang.reflect.Method.invoke (Method.java:255)
      org.apache.catalina.security.SecurityUtil$1.run (SecurityUtil.java:243)
      java.security.AccessController.doPrivileged (AccessController.java:195)
      javax.security.auth.Subject.doAsPrivileged (Subject.java:250)
      org.apache.catalina.security.SecurityUtil.execute (SecurityUtil.java:272)
      org.apache.catalina.security.SecurityUtil.doAsPrivilege (SecurityUtil.java:161)


note The full stack trace of the root cause is available in the Apache Tomcat/5.0 logs.


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Apache Tomcat/5.0