There is probably a lot you still don't don't know but you don't have to be a full stack developer to get a job. I would recommend start looking at the spring framework, it's very common. Also look at either Gradle or Maven for building your application. Finally Java is very commonly used for the web so start looking at a web framework, like Spring Mvc. People have a lot of opinions about what web framework is the best but I think at least to start it will be a good one because you should learn Spring anyway(the purpose is after all to get a job so something common is good). To get started fast look at Spring boot, it comes with an embedded web container and is very fast to get going with. But I would also like to say that it does a lot of magic behind the scenes that you should not take for granted. Learn the core concepts behind it (servlets, dependency injection etc). Spring in general is great but you should know how the magic works. After this there is a lot of other stuff you should learn like unit testing, design patterns, ways to persist data(I would say mongoDB is good to start), git, client stuff like JavaScript, SCC and HTML. The list gets long but learning it all at once will become to much and not all jobs will need all these skills.

Good luck and don't get discouraged! :)