tomcat formAutheticator problem

Hi,
I am having tomcatformAuthentictor problem, when i deploy my application. Apllication deploys successfully but doesnt show login page. I am using JDK1.4(its an old application) and tomcat 5.5.17

following is the stack trace.

04-Jun-2008 13:13:50 org.apache.catalina.authenticator.FormAuthenticator forwardToLoginPage
WARNING: Unexpected error forwarding to login page
org.apache.jasper.JasperException
        at org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:510)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:672)
        at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:463)
        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:398)
        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301)
        at org.apache.catalina.authenticator.FormAuthenticator.forwardToLoginPage(FormAuthenticator.java:315)
        at org.apache.catalina.authenticator.FormAuthenticator.authenticate(FormAuthenticator.java:243)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
        at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
        at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
        at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
        at java.lang.Thread.run(Thread.java:534)

Cant figure out why is this happening. please help

I am also working on authentication only. In my application its working perfectly. Can you please provide the code snippet from web.xml file. It may help to figure out the problem.

Thank you for looking at my problem. Here is the web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee <a href="http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">" target="_blank" rel="nofollow">http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"></a>
    <display-name>Extranet Application</display-name>
    <listener>
    <description>Listener for class Counter.java</description>
    <listener-class>com.oscel.extranet.Counter</listener-class>
  </listener>
  <servlet>
    
    <servlet-name>action</servlet-name>
    <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
    <init-param>
      <param-name>config</param-name>
      <param-value>/WEB-INF/struts-config.xml</param-value>
    </init-param>
    <init-param>
      <param-name>application</param-name>
      <param-value>ApplicationResources</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
 
  <servlet-mapping>
    <servlet-name>action</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>
  
  <session-config>
    <session-timeout>30</session-timeout>
  </session-config>
  
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  
  <error-page>
    <exception-type>java.lang.Exception</exception-type>
    <location>/error.jsp</location>
  </error-page>
  <error-page>
    <error-code>403</error-code>
    <location>/admin/access-denied.jsp</location>
  </error-page>
  <error-page>
    <error-code>404</error-code>
    <location>/index.jsp</location>
  </error-page>
  
  <jsp-config>
    
    <taglib>
      <taglib-uri>/WEB-INF/struts-bean.tld</taglib-uri>
      <taglib-location>/WEB-INF/struts-bean.tld</taglib-location>
    </taglib>
    <taglib>
      <taglib-uri>/WEB-INF/struts-html.tld</taglib-uri>
      <taglib-location>/WEB-INF/struts-html.tld</taglib-location>
    </taglib>
    <taglib>
      <taglib-uri>/WEB-INF/struts-logic.tld</taglib-uri>
      <taglib-location>/WEB-INF/struts-logic.tld</taglib-location>
    </taglib>
    <taglib>
      <taglib-uri>/WEB-INF/struts-nested.tld</taglib-uri>
      <taglib-location>/WEB-INF/struts-nested.tld</taglib-location>
    </taglib>
    <taglib>
      <taglib-uri>/WEB-INF/struts-tiles.tld</taglib-uri>
      <taglib-location>/WEB-INF/struts-tiles.tld</taglib-location>
    </taglib>
 
    <taglib>
      <taglib-uri>http://java.sun.com/jstl/fmt</taglib-uri>
      <taglib-location>/WEB-INF/fmt.tld</taglib-location>
    </taglib>
    <taglib>
      <taglib-uri>http://java.sun.com/jstl/core</taglib-uri>
      <taglib-location>/WEB-INF/c.tld</taglib-location>
    </taglib>
    <taglib>
      <taglib-uri>http://java.sun.com/jstl/sql</taglib-uri>
      <taglib-location>/WEB-INF/sql.tld</taglib-location>
    </taglib>
    <taglib>
      <taglib-uri>http://java.sun.com/jstl/x</taglib-uri>
      <taglib-location>/WEB-INF/x.tld</taglib-location>
    </taglib>
  </jsp-config>
  
  <resource-ref>
    <description>DB Connection</description>
    <res-ref-name>jdbc/extranet</res-ref-name>
    <res-type>javax.sql.DataSource</res-type>
    <res-auth>Container</res-auth>
  </resource-ref>
 
  <security-constraint>
    <web-resource-collection>
      <web-resource-name>Secure access to users</web-resource-name>
      <url-pattern>/*</url-pattern>
    </web-resource-collection>
    <auth-constraint>
      <role-name>superuser</role-name>
      <role-name>admin</role-name>
      <role-name>user</role-name>
    </auth-constraint>
  </security-constraint>
  
  <security-constraint>
    <web-resource-collection>
      <web-resource-name>Secure access to Administrators and Superusers</web-resource-name>
      <url-pattern>/admin/*</url-pattern>
    </web-resource-collection>
    <auth-constraint>
      <role-name>superuser</role-name>
      <role-name>admin</role-name>
    </auth-constraint>
  </security-constraint>
  
  
  <login-config>
    <auth-method>FORM</auth-method>
    <realm-name>JDBC Realm</realm-name>
    <form-login-config>
      <form-login-page>/login.jsp</form-login-page>
      <form-error-page>/loginerror.jsp</form-error-page>
    </form-login-config>
  </login-config>
  <security-role>
    <description>Superuser Role</description>
    <role-name>superuser</role-name>
  </security-role>
  <security-role>
    <description>Admin Role</description>
    <role-name>admin</role-name>
  </security-role>
  <security-role>
    <description>User Role</description>
    <role-name>user</role-name>
  </security-role>
</web-app>

I also faced this issue. But solved by changing the web.xml elements order.
I am not sure but please check your web.xml file only. If you are using eclipse and if there is any mistake in web.xml file, it should highlight the error. I hope this may help you.