Reo

Reo is a top-notch and easily accessible open-source transparent object-relational mapper. If you're currently searching for an OR mapper that you can utilize for your latest Java project, Reo could be well worth considering. It's been expertly designed with Java in mind, and therefore it should slot neatly into your current development environment with minimal fuss.

Something else that sets Reo apart from the competition is that it is based on transparency. This means that if you choose to use it for your next project, you'll be able to use it for every single persistence-based action required in your application. From the start of the project, down to the final testing phase, Reo has you covered.

Another fantastic feature of Reo is that there are active plans to have it ported over to other object-oriented environments beyond just Java. So, if your project crosses over into those areas, you may be able to enjoy the benefits of Reo there as well.

To sum up then, Reo is a quality piece of software that implements its purpose with ease and transparency. It's an enjoyable piece of software to use, and you shouldn't find yourself grappling with any notable issues. Highly recommended!