Comment by vbezhenar

The main problem is Spring Boot and some other Spring projects like Security.

If you would use Spring MVC directly, it is very possible that one could upgrade Spring versions for many years with minimal or no changes at all.

However Spring Boot regularly breaks code. And given the fact that it's very popular, it means that any Java upgrade is pain. You need to rewrite code, sometimes a lot of code.

If you just use JAX-RS, probably simple Spring setup would suffice, but people usually want to slap database, security stuff and other things and everything is provided by Spring, so it's not apples-to-apples comparison.