I have installed Tomcat in Debian from the repositories but I don't know how to control it. There isn't also any systemd service. How do I stop and restart the server?
The service is called tomcat9 not tomcat. Don't you have it installed? You should be able to see it with
tomcat9
tomcat
$ systemctl list-unit-files
and control it like all the other services
$ systemctl start/restart/stop tomcat9