Response from Server Scala with Play - scala

Question

I'm doing my first application with Scala and Play! Where I use a WebSocket exactly like they do in the chatroom example, so far I can send messages to my server but I don't seem to understand where I can "handle" this messages that I get from my client, also I wanted to know if I can send Json Arrays from my server to my client:
#Singleton
class HomeController #Inject()(cc: ControllerComponents)
(implicit actorSystem: ActorSystem,
mat: Materializer,
executionContext: ExecutionContext)
extends AbstractController(cc) {
private type WSMessage = String
private val logger = Logger(getClass)
private implicit val logging = Logging(actorSystem.eventStream, logger.underlyingLogger.getName)
// chat room many clients -> merge hub -> broadcasthub -> many clients
private val (chatSink, chatSource) = {
// Don't log MergeHub$ProducerFailed as error if the client disconnects.
// recoverWithRetries -1 is essentially "recoverWith"
val source = MergeHub.source[WSMessage]
.log("source")
.recoverWithRetries(-1, { case _: Exception ⇒ Source.empty })
val sink = BroadcastHub.sink[WSMessage]
source.toMat(sink)(Keep.both).run()
}
private val userFlow: Flow[WSMessage, WSMessage, _] = {
Flow.fromSinkAndSource(chatSink, chatSource)
}
def index: Action[AnyContent] = Action { implicit request: RequestHeader =>
val webSocketUrl = routes.HomeController.chat().webSocketURL()
logger.info(s"index: ")
Ok(views.html.index(webSocketUrl))
}
def chat(): WebSocket = {
WebSocket.acceptOrResult[WSMessage, WSMessage] {
case rh if sameOriginCheck(rh) =>
Future.successful(userFlow).map { flow =>
Right(flow)
}.recover {
case e: Exception =>
val msg = "Cannot create websocket"
logger.error(msg, e)
val result = InternalServerError(msg)
Left(result)
}
case rejected =>
logger.error(s"Request ${rejected} failed same origin check")
Future.successful {
Left(Forbidden("forbidden"))
}
}
}
}
Btw I'm sending the messages from my client through a Jquery function.
Edit The way I want to handle this messages is by passing them as parameters to a function, the function will return an Array of strings or integers which I want to return to the client

Answer 1

All you need to do is add a flow stage to your between your source and sink which can store in DB and return some other message to clients.
Here's how you can fix the above problem:
Do whatever you want with the received message here.
val flow = Flow[WSMessage].map { element =>
println(s"Message: $element")
element
}
Note that for persisting messages in the database, you will most likely want to use an async stage, roughly:
val flow = Flow[WSMessage].mapAsync(parallelism) { element =>
println(s"Message: $element")
// assuming DB.write() returns a Future[Unit]
DB.write(element).map(_ => element)
}
And finally, you need to add the flow stage to the stream pipeline.
source.via(flow).toMat(sink)(Keep.both).run()