Is this possible to create a web app that will run in a raspberry pi 4 and access it through SSL from the outside world. What interests me is displaying it in a frame in an https site. If it is possible what are the steps I need to follow?
Yes.
It doesn't matter whether the site is served from a supercomputer or a Raspberry Pi.
First step is to configure a host name for the relevant ip. If you don't have a static ip then you will need to use a dynamic dns service such as no-ip.
You will also need to configure the router to forward the port (443) to the rpi.
And you will need a ssl certificate.
Check out this post to learn more about using the Java keytool command, focusing on how to create a keystore, generate a CSR, import certificates, and more.
dzone.com
After that I used the free TrustCore Standard DV certificate that no-ip.com provides with each subscription. When I received it I imported it to the keystore file and I am good to go. Thanks a lot.