This demo is based on servlet demo from oracle sample available here.
I have made few fixes to original demo to make it compatible with current scenario.
Build the application using mvn package and it would produce artefact target/emp-app.war you can then deploy this file on remote/local tomcat (or any other Servlet 3.x Compatible Runtime).
The application uses relative URLs in all request mappings so changing context-root from emp-app to ROOT should never result in ERROR 404.