Simple provider for Keycloak as an example how a simple custom event listener can be implemented. To simulate a more complex implementation a dependency is included and the result is packed as an EAR.
Build the ear using mvn package and then deploy it from example-ear/target/ to e.g. /opt/jboss/keycloak/standalone/.
After server start/restart go to the Admin Console and navigate to Manage/Events/Config and add event-listener-example as Event Listener. Save it and watch your console ;)