Spring is, by far, the most popular framework for application development in the Java ecosystem. By a wide margin. The reason is actually quite simple - it does a lot of things right, and it's getting better and better with each release.
There aren't a lot of technologies with the kind of wide reach, stability and maturity of Spring, that still move fast and innovate. That's a really tough balance to hit, and Spring has been hitting it for over a decade.
Today, Spring, along with Boot, is a polished, modern and highly expressive framework, easily passing the Twitter test. That's where you can actually fit useful functionality into a single tweet :)
So, the popularity of the Spring ecosystem is well deserved. If you're working in Java, you're very likely doing work with Spring.
And, while the Spring ecosystem is quite large and moving fast, the core functionality is actually super stable.
Learning Spring means - learning the core, Spring MVC, persistence, the basics of Spring Security. These are the foundations and, like all good foundations, they're stable and well established.
Simply put, there’s never been a better time to learn and practice and improve your Spring foo in a guided way, coding along with me through each video lesson here.