I’m a web (frontend) developer with 7+ years of experience. I want to become a full stack developer and want to get to know the business side of java. Already know the language and can easily write small CLI or GUI apps (mostly thanks to knowledge of other languages) but have no experience at all with anything business-related. What libraries/solutions would you recommend to me to learn (DB libs, queueing, http server, sockets, etc, anything else)?
Imho, the java aspect of it matters much less than the backend concepts. Are you already familiar with those ?
There’s quite a lot of stuff to learn on the backend and it really depends on which layer you want to focus on. If you’re interested in developing business services then i would recommend writing a restful API (for example for a to-do app) with spring boot and your preferred flavor of SQL database. That covers a lot already. From there you can look at how to scale performance up (caching, queuing, asynchronous).