Java is obviously a well-established language with a substantial community behind it and abundant documentation.
I used the Spring MVC framework and the Spring Tool Suite IDE. Having no experience setting up back-end frameworks, I relied on the suggestions of my colleagues in making this decision. Jackson with Jersey was another option, but we decided Spring would be easier to work with in the end, albeit more complicated to set up.
As a front-end developer, I've never had the occasion to get familier with REST Services or controllers, let alone try to implement them. Now when my back-end colleagues talk about database connections and POJOs (Plain Old Java Objects), I can nod knowingly instead of letting my eyes gloss over. Fortunately, my programmer colleagues were all very helpful in pointing me in the right directions. Deep Mistry (yes, that's his real name) was especially helpful getting me through the Spring setup.
Day two: Kotlin Granny
Developer: Lifford Pinto, Java/Spring guy with his head in the clouds
Given that Kotlin is a fairly young language, it wins coolness points. A new language is a programmer's turn-on.
I don't think it would be fair to say that I liked or disliked it, considering the fact that I spent only a day working with it. It does have enough appeal to make me want to revisit this exercise without the constraint of the do-it-in-a-day deadline. It was easy to set up, and the documentation has several examples to help you get familiar with the language. I appreciated that the Kotlin team was willing to provide us with mentor support even on short notice.
I do most of my development work on Eclipse-based IDEs, but the obvious choice of IDE for Kotlin was JetBrains IntelliJ. I used the Kara Framework to quickly set up an MVC application. It's hard to say if this was "quintessential" or not -- Kotlin hasn't been around long enough. Regardless, this was easy to work with and set up. I couldn't easily figure out how to communicate to the front end via JSON, so I quickly switched to hack string manipulation to get 'er done. Talking to the database was easy via Kotlin's JDBC library.