Upgrading from Tomcat 7 to Tomcat 8
When we upgraded from Apache Tomcat 7.0.21 to 7.0.56, all that we did, was copy over every single file in the TOMCAT_HOME/conf directory into the new installation and everything worked perfectly. When I did the same thing upgrading to Tomcat 8.0.15, it blew apart. Tomcat would not even start. The exception in the logs was:
The fix was to find the original server.xml and splice in our local stuff into it -- like the context and the appBase and the listening port. Once we did that, it worked like a charm.
Hope this helps someone.