title: javax.servlet.ServletException - how could i get to the cause?
body: <p>i'm getting a very strange error while opening one of the pages in my web app. The application is built on Seam 2.2 and is using JSF (RichFaces) in the presentation layer. I run it on Tomcat 6.</p>
  
  <p>In logs everything looks fine - each next JSF Phase executes normally, and after the last one, there is this moment when the request starts processing for the SEAM debug page...</p>
  
  <p>And this is the stack trace i see on the debug page (nothing is logged):</p>
  
  <p>Exception during request processing:
  Caused by javax.servlet.ServletException with message: "Servlet execution threw an exception"</p>
  
  <pre><code>org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:313)
  org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:83)
  org.jboss.seam.web.IdentityFilter.doFilter(IdentityFilter.java:40)
  org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
  org.jboss.seam.web.MultipartFilter.doFilter(MultipartFilter.java:90)
  org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
  org.jboss.seam.web.ExceptionFilter.doFilter(ExceptionFilter.java:64)
  org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
  org.jboss.seam.web.RedirectFilter.doFilter(RedirectFilter.java:45)
  org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
  org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:178)
  org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:290)
  org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:388)
  org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:515)
  org.jboss.seam.web.Ajax4jsfFilter.doFilter(Ajax4jsfFilter.java:56)
  org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
  org.jboss.seam.web.LoggingFilter.doFilter(LoggingFilter.java:60)
  org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
  org.jboss.seam.web.HotDeployFilter.doFilter(HotDeployFilter.java:53)
  org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
  org.jboss.seam.servlet.SeamFilter.doFilter(SeamFilter.java:158)
  org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
  org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  pl.mgibowski.alterium.util.LoggingFilter.doFilter(LoggingFilter.java:18)
  org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
  org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
  org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
  org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:465)
  org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
  org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
  org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
  org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
  org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852)
  org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
  org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
  java.lang.Thread.run(Thread.java:619)
  </code></pre>
  
  <p>Exception without any cause...</p>
  
  <p>I was trying to catch the exception with my custom Filter (LoggingFilter.java that you can see on the strack trace), using this code:</p>
  
  <pre><code>try {
              filterChain.doFilter(servletRequest, servletResponse);
          }
          catch (Throwable e) {
              e.printStackTrace();
              System.out.println("Stack trace:");
              System.out.println(e.getStackTrace());
              System.out.println("Cause:");
              System.out.println(e.getCause());
          }
  </code></pre>
  
  <p>But it doesn't catch anything, the line 18 from the stack trace is this one:</p>
  
  <pre><code>filterChain.doFilter(servletRequest, servletResponse);
  </code></pre>
  
  <p>nothing gets caught by the try block.</p>
  
  <p>Anybody has any ideas about how could i get closer to the real cause?</p>