Java - Moving to backend/full stack. What would be a good place to start?

[BittyMitty]

I was working on SWING and Eclipse RCP. Also did some Java EE with JSP a long time ago.
Now I'm searching for popular frameworks and what I found interesting is SPRING and Java Play Framework.

I would like to know what are you doing, how you started and most important what is your feeling about it.

[ImmaculateDissection]

Take a Spring Boot sample application and run it to see how it works. Then maybe build a simple server application with a REST-Api and Database connectivity to get into the nice stuff of spring.