Sources

Sources are a special kind of Resolvables: they know from which Endpoints they should be resolved. In this example our Sources trait is a slice of cake that includes Endpoints seen previously and JsonRules, which we’ll define in the next section.

import resolvable.Source
import play.api.data.mapping.json.Rules._

trait Sources { self: Endpoints with JsonRules ⇒

  def book(id: String): Resolvable[Book] =
    // try RemoteBook1 first
    Source[Book].from(RemoteBook1(id)) orElse
    // fallback to RemoteBook2
    Source[Book].from(RemoteBook2(id))

  def author(id: String): Resolvable[Author] =
    Source[Author].from(RemoteAuthor(id))

}

That was easy... but how does it know how to load Books from, say, RemoteBook1, which fetches JsValue? Good question. We need some deserialization logic. We’ll use the cutting edge Play 2.3 validation API!