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)?