[displaytag-user] Export Error

[Bussie, Andre D]

I just installed display tag. I’m try to use the export function however when I click on the Excel export option I get the following error message java.lang.NullPointerException   I configured my web.xml as requested in the installed doc   web.xml filter>    <filter-name>ResponseOverrideFilter</filter-name>     <filter-class>org.displaytag.filter.ResponseOverrideFilter</filter-class>   </filter>   <filter-mapping>     <filter-name>ResponseOverrideFilter</filter-name>     <url-pattern>/action/*</url-pattern>   </filter-mapping>   <filter-mapping>     <filter-name>ResponseOverrideFilter</filter-name>     <url-pattern>*.jsp</url-pattern>   </filter-mapping>   What is causing this? Any help?   Thanks is advance