Since you say you don't have much recent work with J2EE technologies, I would suggest getting a REST lib and learning to develop RESTful services, demand is hig

Since you say you don't have much recent work with J2EE technologies, I would suggest getting a REST lib and learning to develop RESTful services, demand is high for back-end REST developers and you can be spitting out JSON in a day or two and other formats shortly there after. If you have Java experience and can stand up a REST service, you will find something.