sderosiaux / ultra-slim-play-scala

Play Framework application reduced to a strict minimum

Ultra-slim-play-app

The idea is to start an Play! application as any classic application, meaning, without app/ or application.conf magic. It's inspired from https://github.com/lloydmeta/slim-play, but it's going further by removing more Play! dependencies.

Basically, everything is in one file, a Main, without external references to any configuration. It doesn't even run in app/ anymore, but it's just a classic Scala Main extends App to start.

Play! version: 2.5.10

Code

Here is the whole code in src:

object Main extends App {

  val context = ApplicationLoader.Context(Environment.simple(), None, new DefaultWebCommands(), Configuration.from(Map(
    "play.crypto.secret" -> "changeme",
    "play.crypto.provider" -> "",
    "play.crypto.aes.transformation" -> "",
    "play.http.context" -> "/",
    "play.http.parser.maxMemoryBuffer" -> "2MB",
    "play.http.parser.maxDiskBuffer" -> "10MB",
    "play.http.actionComposition.controllerAnnotationsFirst" -> false,
    "play.http.actionComposition.executeActionCreatorActionFirst" -> false,
    "play.http.cookies.strict" -> true,
    "play.http.session.cookieName" -> "",
    "play.http.session.secure" -> true,
    "play.http.session.maxAge" -> null,
    "play.http.session.httpOnly" -> true,
    "play.http.session.domain" -> "",
    "play.http.flash.cookieName" -> "",
    "play.http.flash.secure" -> true,
    "play.http.flash.httpOnly" -> true,
    "play.http.forwarded" -> Map("version" -> "x-forwarded", "trustedProxies" -> List()),
    "play.akka.config" -> "akka",
    "play.akka.actor-system" -> "hello",
    "akka" -> Map()
  )))

  val app = new BuiltInComponentsFromContext(context) {
    import play.api.routing.Router
    import play.api.routing.sird._

    override def router = Router.from {
      case GET(p"/hello/$to") => Action {
        Results.Ok(s"Hello $to")
      }
    }
  }.application

  Server.withApplication(app, ServerConfig(port = Some(8000))) { _ =>
    new CountDownLatch(1).await()
  }
}

All those properties are the strict minimum for Play! to start. (it's mostly HttpConfiguration()) I'm sure we can bypass that and provide the configuration using the default case classes, but I didn't look any further. You can PR if you find out.

It starts the application manually and wait indefinitely at the end (otherwise the program exits, we need something blocking).

How to

Start the Main yourself in Intellij or however you want. You'll see some debug logs (mostly netty) and the HTTP server starting:

02:29:55.975 [main] INFO play.core.server.NettyServer - Listening for HTTP on /0:0:0:0:0:0:0:0:8000

It works!

$ curl http://localhost:8000/hello/you
Hello you

Note

There is still an empty application.conf in conf/ because Play! checks for its existence. :-(