How does RequestInterceptor work?

[David M. Rosner]

Hello,

I have a package that I've placed in a JAR file within the $TOMCAT_HOME/lib 
directory. Then I updated the server.xml file to use a class file within 
this package instead of the default Tomcat version. Yet, when i run tomcat 
I get a 'ClassNotDefined' exception. What do I need to do to get Tomcat to 
recognize a class that I define within a RequestInterceptor block in the 
server.xml file?

Is there any documentation out there that explains how the server.xml file 
is used?

Thanks!