Error when using Try/Catch in Play Framework with Websocket - scala

Question

I am using web sockets with Play Framework in Scala. I would like to use Try/Catch functionality in my project for catching some Exceptions like Server Exception, Network Exception and etc.
What I did :
WebSocketController.scala
object LoginWS {
def props(out: ActorRef) = Props(new LoginWS(out))
}
class LoginWS(out: ActorRef) extends Actor {
def receive = {
case json_req: JsObject =>
var user_name = (json_req \ "user_name").as[String]
var password = (json_req \ "password").as[String]
var source = (json_req \ "source_type").as[String]
var result = UserLogin.authenticateUser(user_name, password).isDefined
var userID: Int = 0;
if(result) {
userID = UserLogin.getUserRole(user_name, password)
val login_status : String = "Success"
out ! Json.toJson(JsObject(Seq("login_status" -> JsString(login_status), "user_id" -> JsNumber(userID))))
}
else {
val login_status : String = "Failure"
out ! Json.toJson(JsObject(Seq("login_status" -> JsString(login_status), "user_id" -> JsNumber(userID))))
}
}
}
object WebSocketController extends Controller {
def login = WebSocket.acceptWithActor[JsValue, JsValue] { request =>
out => LoginWS.props(out)
}
}
What I tried :
I have used this answer posted by Ende Neu but it shows not found: value APIAction. Note: I added APIAction in routes file too
Code :
class LoginWS(out: ActorRef) extends Actor {
def receive = APIAction { request
case json_req: JsObject =>
.....
....//code here
}
}
object WebSocketController extends Controller {
def login = WebSocket.acceptWithActor[JsValue, JsValue] { request =>
out => LoginWS.props(out)
}
def APIAction(f: Request[AnyContent] => Result): Action[AnyContent] =
Action { request =>
Try(f(request))
.getOrElse(
InternalServerError(Json.obj("code" -> "500", "message" -> "Server error"))
)
}
}
Please help me to implement Try/Catch functionality in Web socket

Answer 1

Login request is handled within actor and I think you should handle your errors there. If you want to catch all exceptions instead of explicitly handling what could go wrong, I suggest doing the following
object SomeUtils {
def catchAll[A](out: ActorRef)(f: => A): Unit = {
val message = Try(f).getOrElse(Json.obj("code" -> "500", "message" -> "Server error"))
out ! message
}
}
import SomeUtils._
class LoginWS(out: ActorRef) extends Actor {
def receive = {
case json_req: JsObject => catchAll(out) {
val userName = (json_req \ "user_name").as[String]
val password = (json_req \ "password").as[String]
val authenticated = UserLogin.authenticateUser(userName, password).isDefined
if (authenticated) {
val role = UserLogin.getUserRole(userName, password)
Json.obj("login_status" -> "Success", "result" -> role)
}
else {
Json.obj("login_status" -> "Failure", "result" -> 0)
}
}
}
}
When handling jsonReq use catchAll method that would expect to get a receiver of the result and this result that could throw an Exception. In case of Exception it would use a default message with internal server error, and send this message to the receiver.
You could also make the out parameter implicit to skip putting it everywhere. Also your code is not really in scala style. Using vars etc...
If json sent to WS couldn't be parsed it would throw exception before reaching your code, solution can be found here:
How do I catch json parse error when using acceptWithActor?