如何在Akka Scala的HttpResponse中设置`Set-Cookie`标头？

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)