I am a Java dev and Spring user for about 10 years now.

If you want to learn how Spring framework and Spring boot works, the best thing to do is build your own library and then learn to add it to a new spring boot service.

https://www.baeldung.com/spring-boot-custom-starter

Depending on which AI tool you are using, you can also get it to debrief what it is doing and what layer of the Spring architecture it is using (lifecycle, bean scope, is it using auth/messaging/data middleware etc)

Also here is a service I have built with Claude code along with a sample Spring boot service

https://github.com/tomaytotomato/spring-data-solr-lazarus

It is a demo to show that I could get Apache Solr working in the latest version of Spring Framework 7 and Spring Boot 4. There is a sample application in there for a bookstore you can play around with.