I was trying to insert websocket API's in a project that uses REST API's using scala.When I compile the program this error occurs - scala

Question

I'm trying to establish a websocket connection. I'm trying this in a already created project. And this error occurs.
Type mismatch, expected: Flow[HttpRequest, HttpResponse, Any], actual:
server.Route
The error occurs at route
val binding = Http().bindAndHandle(route, interface, port)
println(s"Server is now online at http://$interface:$port\nPress RETURN
to stop...")
StdIn.readLine()
binding.flatMap(_.unbind()).onComplete(_ => actorSystem.terminate())
println("Server is down...")
val route=path("ws-echo") {
(get) {
val requestHandler: HttpRequest ⇒ HttpResponse = {
case req#HttpRequest( GET, Uri.Path( "/greeter" ), _, _, _ ) ⇒
req.header[UpgradeToWebSocket] match {
case Some( upgrade ) ⇒ upgrade.handleMessages(
greeterWebSocketService
)
case None ⇒ HttpResponse( 400, entity = "Not a valid websocket
request!" )
}
case r: HttpRequest =>
r.discardEntityBytes()
HttpResponse( 404, entity = "Unknown resource!" )
}
}
}
override implicit val system = ActorSystem()
override implicit val executor = system.dispatcher
override implicit val materializer = ActorMaterializer()
override val logger = Logging(system, getClass)
implicit val mat: Materializer
implicit val actorSystem = ActorSystem("akka-system")
val router: server.Route = routes
val config = ConfigFactory.load()
val interface = config.getString("app.interface")
val port = config.getInt("app.port")
Http().bindAndHandle(router, Configuration.httpInterface,
Configuration.httpPort)

Answer 1

I suspect you're getting this error on the line val binding = Http().bindAndHandle(route, interface, port), is that correct?
Indeed bindAndHandle expects a Flow:
def bindAndHandle(
handler: Flow[HttpRequest, HttpResponse, Any],
interface: String,
port: Int = DefaultPortForProtocol,
connectionContext: ConnectionContext = defaultServerHttpContext,
settings: ServerSettings = ServerSettings(system),
log: LoggingAdapter = system.log)(implicit fm: Materializer
): Future[ServerBinding]
So why do so many examples show passing in a Route? The 'magic' here that there's an implicit conversion available to turn a Route into a Flow.
This is basically an implementation detail, you normally shouldn't have to care about this, but the implicit conversion is route2HandlerFlow:
implicit def route2HandlerFlow(
route: Route
)(
implicit routingSettings: RoutingSettings,
parserSettings: ParserSettings,
materializer: Materializer,
routingLog: RoutingLog,
executionContext: ExecutionContext = null,
rejectionHandler: RejectionHandler = RejectionHandler.default,
exceptionHandler: ExceptionHandler = null
): Flow[HttpRequest, HttpResponse, NotUsed]
As you can see, this implicit conversion requires some other implicit values to be available. I suspect you are missing one of those. I think it might be enough to introduce an implicit Materializer, could you give that a try?