The Play WebSocket API allows the use of Actors to define the behavior. Let's build the WebSocket application that replies with the reverse of a given String once it's connected. We can do this by slightly modifying our Reverser Actor to have an argument as the reference of the Actor to which it can/must send messages, as shown here:
class Reverser(outChannel: ActorRef) extends Actor {
def receive = {
case s: String => outChannel ! s.reverse
}
}
object Reverser {
def props(outChannel: ActorRef) = Props(classOf[Reverser], outChannel)
}The websocket can then be defined in a controller as follows:
def websocket = WebSocket.acceptWithActor[String, String] {
request => out =>
Reverser.props(out)
}Finally, we make an entry in the routes file:
GET /wsActor controllers.Application.websocket
We can now send messages through the WebSocket when the application is running using a browser plugin.
Now, lets try to implement dbWebSocket using this method:
def dbCommunicator = WebSocket.acceptWithActor[JsValue, JsValue] {
request => out =>
WebSocketChannel.props(out)
}Here, WebSocketChannel is defined as follows:
class WebSocketChannel(out: ActorRef)
extends Actor with ActorLogging {
val backend = Akka.system.actorOf(DBActor.props)
def receive: Actor.Receive = {
case jsRequest: JsValue =>
backend ! convertJsonToMsg(jsRequest)
case x:DBResponse =>
out ! x.toJson
}
}
object WebSocketChannel {
def props(out: ActorRef): Props =
Props(classOf[WebSocketChannel], out)
}The
convertJsonToMsg method is responsible for translating JSON to a format that is accepted by the DBActor.