Please Help:Getting a ServletFilter Sample working

Question

Hi,
I am testing a Servlet Filter usage. And somehow, my application doesn't
even start in Tomcat 5.5. Please help me in debugging, where I am going
wrong.
I am also using Struts 5.5 in this application
Here is what did:
SampleFilter.java
package app;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class SampleFilter implements Filter {
private FilterConfig config = null;
public void init(FilterConfig config) throws ServletException {
this.config = config;
public void destroy() {
// config = null;
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException
          // creating a dummy session to check if i am hitting it
HttpSession session =((HttpServletRequest) request).getSession( );
session.setAttribute("ReallyValue", "Testesttest");
chain.doFilter(request, response);
Snippet from web.xml that i added:
<filter>
          <filter-name> SampleFilter </filter-name>
          <filer-class> app.SampleFilter </filer-class>
</filter>
          <filter-mapping>
          <filter-name> SampleFilter</filter-name>
          <url-pattern>/*</url-pattern>
</filter-mapping>
Log Trace in Tomcat 5.5
Oct 26, 2007 2:46:48 PM org.apache.catalina.core.ApplicationContext log
INFO: HTMLManager: list: Listing contexts for virtual host 'localhost'
Oct 26, 2007 2:46:49 PM org.apache.catalina.core.ApplicationContext log
INFO: HTMLManager: list: Listing contexts for virtual host 'localhost'
Oct 26, 2007 2:46:51 PM org.apache.catalina.core.ApplicationContext log
INFO: HTMLManager: start: Starting web application at '/FormTrial'
Oct 26, 2007 2:46:53 PM org.apache.catalina.core.StandardContext filterStart
SEVERE: Exception starting filter SampleFilter
java.lang.NullPointerException
     at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:200)
     at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:304)
     at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:77)
     at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3634)
     at org.apache.catalina.core.StandardContext.start(StandardContext.java:4217)
     at org.apache.catalina.manager.ManagerServlet.start(ManagerServlet.java:1175)
     at org.apache.catalina.manager.HTMLManagerServlet.start(HTMLManagerServlet.java:527)
     at org.apache.catalina.manager.HTMLManagerServlet.doGet(HTMLManagerServlet.java:104)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
     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.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
     at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:524)
     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:595)
Oct 26, 2007 2:46:53 PM org.apache.catalina.core.StandardContext start
SEVERE: Error filterStart
Oct 26, 2007 2:46:53 PM org.apache.catalina.core.StandardContext start
SEVERE: Context [FormTrial] startup failed due to previous errors
Oct 26, 2007 2:46:53 PM org.apache.catalina.core.ApplicationContext log
INFO: HTMLManager: list: Listing contexts for virtual host 'localhost'

Answer 1

Crosspost: http://forum.java.sun.com/thread.jspa?threadID=5230626&messageID=9942214#9942214
Please stop posting the same question all over the place. If you must post in different forums, then just put up a link to the original post so that everyone answers at one place.
And someone has already given you a suggestion at the thread linked above, have you tried that out? If not, then why not? If yes, then what was the outcome? It's rude not to reply and even more insulting to ignore and then crosspost.