sudo keytool -genkey -alias tomcat -keyalg RSA -keystore /etc/tomcat8/keystore
sudo vi /etc/tomcat8/server.xml
find and uncomment lines with SSL
add some attributes:
keystoreFile="/etc/tomcat8/keystore"
keystorePass="password"
restart tomcat to pick up the changes
sudo systemctl restart tomcat8
open browser and check
https://localhost:8443