Note: this is a somewhat advanced topic, most users safely can ignore this

While one can really take advantage of most play features while building a full application from scratch using play, it's very easy to drop play into existing sbt/maven projects and with just a little work use it as a REST/HTTP library. Below you can see how to do that.

Because play2's core is written in scala, the easiest way to provide a Java API is by creating the required API in scala.

In practice it means that one needs to extend GobalSettings as Global in the global name space. GobalSettings has a method def onRouteRequest(request: RequestHeader): Option[Handler] that's handling play's routing. Once an alternative implementation is in place, play can be used as a REST/HTTP library!

an annotation based basic implementation can be found here for an example.