How to set `Set-Cookie` header in HttpResponse in Akka Scala? - scala

Question

I have the following route in my app:
val myRoute = Route { context =>
val handler = Source.single(getRequest(context))
.via(flow(server, port))
.runWith(Sink.head).flatMap { r =>
// Add cookie to response depending on certain preconditions
context.complete(r)
}
}
My problem is that I can't use the out-of-the-box setCookie method (or can I?) because I am inside a route, so I will get a type error. I thought about manually adding a header element to the HttpResponse (in the example above r), but that is quite cumbersome.
Any ideas how I can easily add the Set-Cookie header element?

Answer 1

setCookie Directive
A Route is just a type definition: (RequestContext) => Future[RouteResult]. Therefore you can use function composition to add a cookie to the HttpResponse coming from the downstream service.
First create a forwarder that utilizes the predefined flow:
val forwardRequest : HttpRequest => Future[HttpResponse] =
Source
.single(_)
.via(flow(server, port))
.runWith(Sink.head)
Then compose that function with getRequest and a converter from HttpResponse to RouteResult:
val queryExternalService : Route =
getRequest andThen forwardRequest andThen (_ map RouteResult.Complete)
Finally, set the cookie:
val httpCookie : HttpCookie = ??? //not specified in question
val myRoute : Route = setCookie(httpCookie)(queryExternalService)
Manual Addendum in Route
You can manually set the cookie:
val updateHeaders : (HttpHeader) => (HttpResponse) => HttpResponse =
(newHeader) =>
(httpResponse) =>
httpResponse withHeaders {
Some(httpResponse.headers.indexWhere(_.name equalsIgnoreCase newHeader.name))
.filter(_ >= 0)
.map(index => httpResponse.headers updated (index, newHeader) )
.getOrElse( httpResponse.headers +: newHeader )
}
...
.runWith(Sink.head).flatMap { response =>
context complete updateHeaders(httpCookie)(response)
}
Pure Flow
You can even avoid using Routes altogether by passing a Flow to HttpExt#bindAndHandle:
val myRoute : Flow[HttpRequest, HttpResponse, _] =
flow(server,port) map updateHeaders(httpCookie)