Connecting to PostgreSQL from Tomcat 7 on OpenShift

I'm using a free OpenShift account to host a small site, and had some trouble getting a connection to my PostgreSQL cartridge from my Tomcat 7 (JBoss EWS 2.0) cartridge. As often happens, the act of asking the question made me think of a few additional solutions to explore, but I ended up posting the question then heading to OpenShift's support page to send a question. Like StackOverflow, OpenShift's contact page starts suggesting articles when you type in a subject, and that's how I found the article that describes their JNDI DataSources exposed by Tomcat.

Deploying a Gradle webapp project in Spring Tool Suite

There's not a lot of documentation on how to configure a Gradle webapp project to deploy to e.g. tc Server in Spring Tool Suite, but based on a recent Spring forum post, it was easy.