json-home-client

No-magic Scala client to consume JSON home documents like this:

{
  "resources": {
    "http://spec.example.org/rels/artists": {
      "href": "/artists"
    },
    "http://spec.example.org/rels/artist": {
	  "href-template": "/artists/{artist-id}",
      "href-vars": {
        "artist-id": "http://spec.example.org/params/artist"
      }
	}
  }
}

The json-home-client regularly loads json home documents from json home document providers, and caches them in memory. When your application retrieves some information from this json-home-client, the cached json home documents are used so that there'll be no network roundtrip.

This library was built for Play! Framework 2.5.x projects and uses Play's WS client and Play's JSON library.

If you're looking for the Play 2.3.x version check out the play-2.3.x branch.

Installation

You must add the json-home-client to the dependencies of the build file, e.g. add to build.sbt:

libraryDependencies += "de.kaufhof" %% "json-home-client" % "3.0.0"

It is published to maven central for 2.11.

Usage

At first you setup the JsonHomeService for various hosts that provide json home documents. The first host serves a json home like the one shown above.

import de.kaufhof.jsonhomeclient._

// Specify which service/host provides which link relations
// By default, json home docs are assumed to be served from `/.well-known/home`.
val host1 = JsonHomeHost("http://some.host", Seq(
  // A link relation without params
  DirectLinkRelationType("http://spec.example.org/rels/artists"),
  // A link relation with template params
  TemplateLinkRelationType("http://spec.example.org/rels/artist")
))

// Create the client, it loads the json home doc from the host
//Make sure to shutdown the ActorSystem after usage
implicit val system = ActorSystem()
implicit val materializer = ActorMaterializer()
val client1 = new JsonHomeClient(host1)

// Create the cache, it will regularly (using the Akka scheduler) load json home doc
// using the client. The initialTimeToWait is used for requests when the schedule did not yet
// kick in (might happen e.g. in tests) so that the json home doc was not yet requested/loaded.
// In this case the json home doc is directly loaded from the client and the cache will wait for
// the result using the given `initialTimeToWait`.
val cache1 = new JsonHomeCache(client1, updateInterval = 5 minutes, initialTimeToWait = 10 seconds)

// The json home service, the interface for applications, set up with several json home caches
val jsonHomeService = JsonHomeService(Seq(cache1, cache2, ...))

Once the json home service is set up, you can use it to retrieve links for link-relations.

// Example 1: Get a link relation that does not expect template params
jsonHomeService.getUrl(
  host1,
  DirectLinkRelationType("http://spec.example.org/rels/artists")
) == Some("/artists")

// Example 2: Some link relation that expects template params
jsonHomeService.getUrl(
  host1,
  TemplateLinkRelationType("http://spec.example.org/rels/artist"),
  Map("artist-id" -> "acdc")
) == Some("/artists/acdc")

License

The license is Apache 2.0, see LICENSE.