Working example of spring boot with embedded tomcat running ssl with a self-signed cert from project root, keystore.p12, created with:
keytool -genkey -alias tomcat -storetype PKCS12 -keyalg RSA -keysize 2048 -keystore keystore.p12 -validity 3650
Example uses password localhost.
See src/test/java/demo/SampleTomcatApplicationTests.java