Running Play WS standalone, without a Play App. Works with Maven builds nicely. The top way to make REST calls in Scala, in my opinion.

output.txt

Here are the first ten Planet Scala titles:
Planet Scala
Big Data Engineer / Data Scientist at Recruit IT (Full-time)
Functional Jobs: Search 'scala'
Mobile Enterprise Integration with Scala, MongoDB and Swagger
Janx Spirit
Scala: Next Steps
Scala 2.11.2 is now available!
Scala for Java Developers
Relentless Scaling
Play 2.3 Applications on OpenShift

Process finished with exit code 0

pom-dependency.xml

    <repositories>
        <repository>
            <id>typesafe</id>
            <name>typesafe-releases</name>
            <url>http://repo.typesafe.com/typesafe/releases</url>
        </repository>
    </repositories>
    <dependencies>
        <dependency>
            <groupId>com.typesafe.play</groupId>
            <artifactId>play-ws_2.11</artifactId>
            <version>2.3.3</version>
        </dependency>
    </dependencies>

WSWithoutPlayApp.scala

package com.scalawilliam.example.play

import play.api.libs.ws._

/**
 * Play's Scala WS library is very very cool. Provides you with plenty niceties.
 * See more: https://www.playframework.com/documentation/2.3.x/ScalaWS
 *
 * Unfortunately it by default requires a Play application context.
 * But you do not necessarily always want that.
 *
 * William Narmontas, Scala Consultant, London. UK
 * https://www.scalawilliam.com/
 */
object WSWithoutPlayApp extends App {

  class StandaloneWSAPI(wsClientConfig: WSClientConfig = DefaultWSClientConfig()) extends WSAPI with java.io.Closeable {

    import play.api.libs.ws.ning.{NingWSClient, NingAsyncHttpClientConfigBuilder}

    lazy val configuration = new NingAsyncHttpClientConfigBuilder(wsClientConfig).build()
    lazy val ningWsClient = new NingWSClient(configuration)
    override val client: WSClient = ningWsClient

    override def url(url: String): WSRequestHolder = client.url(url)

    def close(): Unit = {
      ningWsClient.close()
    }

  }

  val standaloneWSAPI = new StandaloneWSAPI()

  // Standard Play-style WSAPI
  val wsAPI: WSAPI = standaloneWSAPI

  def holder = {
    wsAPI.url("http://www.planetscala.com/atom.xml")
      .withHeaders("Accept" -> "application/xml")
      .withRequestTimeout(10000)
  }

  import scala.concurrent._
  import scala.concurrent.duration._
  import scala.concurrent.ExecutionContext.Implicits.global
  import scala.concurrent.Await

  def getPlanetScalaTitles: Future[Seq[String]] = {
    holder.get().map(_.xml \\ "title" map (_.text))
  }

  println("Here are the first ten Planet Scala titles:")
  try {
    Await.result(getPlanetScalaTitles, 10.seconds) take 10 foreach println
  } finally {
    // required, else there'll be threads hanging around
    // you might not care to do this though.
    standaloneWSAPI.close()
  }

}