I love playing with new technologies. Especially if they are sweet and simple to use. One of those is definitely jOOQ.
jOOQ is a library for working with database in Java. One of its main goals is to create user-friendly, database-first API that would allow you to write type-safe queries in a SQL format.
What is the use case for this? You have some specific SQLs that would be too awkward to write in JPA or you want to have more control on what queries are executed. Or you have simple web services that manipulates data around database and you don't want to use JPA/Hibernate.
I reckon you have looked at the jOOQs project page, but I have something special as well. At our company we have 'tech sessions' from time to time when we explore new technologies and I have one prepared for jOOQ, so be sure to check it out on my Github page.
One last note: Is jOOQ ready for production? Currently no. Will it be? Maybe yes, but still... It is not an open-source, therefore it will have harsh times fighting its position on the market.