Spray routing 404 response

Question

I have a service which returns an Option[ProductDoc] in a Future (as an akka ask)

How do I respond in spray routing so that a valid product repsonds with a product but an unknown but well formed one returns a 404?

I want the code to fill in the gap here :

get {
    path("products" / PathElement) { productID:String =>
      val productFuture = (productService ? ProductService.Get(productID)).mapTo[Option[ProductDoc]]

      // THE CODE THAT GOES HERE SO THAT
      // IF PRODUCT.ISDEFINED RETURN PRODUCT ELSE REJECT

    }
}

The only way I can get to work is with this abomination :

get {
    path(PathElement) { productID:String =>
      val productFuture = (productService ? ProductService.Get(productID)).mapTo[Option[ProductDoc]]
      provide(productFuture).unwrapFuture.hflatMap {
        case x => provide(x)
      } { hResponse:shapeless.::[Option[ProductDoc], HNil] =>
        hResponse.head match {
          case Some(product) => complete(product)
          case None => reject
        }
      }
    }
  }

This can't be the correct way to achieve this, surely? This seems like a pretty simple pattern that must have been solved by someone already!

Answer 1

Spray already has support for your use case: An option value None is marshalled to an EmptyEntity by default. This is probably what you were seeing before you made any changes: a 200 with an empty document. There's a directive which converts an empty document into a 404, rejectEmptyResponse, which you wrap around parts of your route where you want this behavior.

Your route would then look just like this:

  rejectEmptyResponse {
    path("products" / PathElement) { productID:String =>
      val productFuture = // same as before
      complete(productFuture)
    }
  }

Of course, you can put the rejectEmptyResponse inside the path depending on whether you want to wrap more route parts with it.

More info:

• https://github.com/spray/spray/blob/master/spray-routing/src/main/scala/spray/routing/directives/MiscDirectives.scala#L117
• http://spray.io/documentation/spray-routing/key-concepts/rejections/#empty-rejections.