As I usually say, it depends. You already know Java/OOP and done PHP. So got exposure into web, which is good. Going by this statement, it is pretty easy to learn Spring Boot. In fact, Spring Boot feels like Laravel with Composer. It's that easy.
Not much of that configuration crap and it is easy to get started with. I suggest you to start develop simple todo list application using Spring Boot. That will give you the clear idea about how easy it is while you cover all basic aspect of Spring Boot.