Using drools-guvnor (5.5.0) When starting Tomcat the catalina.yyyy-MM-dd.log file shows this warning.
INFO: validateJarFile(/.../tomcat/apache-tomcat-7.0.35/webapps/drools-guvnor/WEB-INF/lib/jboss-servlet-api_3.0_spec-1.0.0.Final.jar) - jar not loaded. See Servlet Spec 2.3, section 9.7.2. Offending class: javax/servlet/Servlet.class
When I moved the offending jar file to /tmp directory, shutdown and restarted Tomcat, the message did not appear in the log. Guvnor *seems* to be working.
Just exclude the .jar from the .war. Tomcat already provides the Servlet apis, so there is no need to include them in Guvnor.
Hope it helps,