Newbie question with tomcat

[abenstex]

Hi,

i am running tomcat 4 with jdk5 on debian and am supposed to install a webapp. So i copied everything into a folder but when i try to access the webapp i get the following error (output from the respective log file):

2006-05-31 14:00:38 default: init
2006-05-31 14:00:38 DatabaseManager: init
2006-05-31 14:00:38 DatabaseManager: Connecting to:jdbc:mysql://localhost/<database>gutenberg
2006-05-31 14:00:39 DatabaseManager: Connection established
2006-05-31 14:00:39 DatabaseManager: DB-Name is:MySQL
2006-05-31 14:00:39 DatabaseManager: set DB-Type to MySQL
2006-05-31 14:00:39 DatabaseManager: DBM registered
2006-05-31 14:00:39 StandardWrapper[/conex:invoker]: Loading container servlet invoker
2006-05-31 14:00:39 invoker: init
2006-05-31 14:00:39 jsp: init
2006-05-31 14:02:22 jsp: init
2006-05-31 14:02:23 StandardWrapperValve[jsp]: Servlet.service() for servlet jsp threw exception
org.apache.jasper.JasperException: Can't find ConceptExtractorServlet in Session Context
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:254)

What is the reason for this. The respective class file is in the WEB-INF folder in the right directory...