Scala Nashorn Interaction

By William "Scala William" Narmontas

Nashorn is a built-in Java 8 JavaScript engine.

You can browse all the Scala code relating to this here: GitHub repository

Scala 2.12 & Java 8 are wonderful together. Let's have a look!

Main code

import javax.script.ScriptEngineManager

import scala.beans.BeanProperty

object NashornScalaInteraction extends App {

  /** Creates .setTransformer() and .getTransformer() which Nashorn can access **/
  /** Nashorn supports working with SAM directly, so Scala methods interoperate directly with JavaScript **/
  @BeanProperty
  var transformer: String => String = { str => str.trim }

  configureArguments()

  printOutput()

  def printOutput(): Unit = {
    List("1", "2", " 3 ").map(transformer).foreach(println)
  }

  def configureArguments(): Unit = {
    val scriptingEngine = new ScriptEngineManager().getEngineByName("javascript")
    scriptingEngine.put("me", this)
    args.sliding(2).collect {
      case Array("--js", command) =>
        command
    }.foreach(scriptingEngine.eval)
  }
}

Running

$ sbt stage
...
$ ./target/universal/stage/bin/scala-nashorn-config --js 'me.transformer = function(x) x + x;'
11
22
 3  3

Build

build.sbt

scalaVersion := "2.12.1"
enablePlugins(JavaAppPackaging)

project/snp.sbt

addSbtPlugin("com.typesafe.sbt" % "sbt-native-packager" % "1.1.4")

Well, that was easy!

Never ever forget that you're in the Java Land ;)

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#Scala #Nashorn #JVM #Java interaction. SO SIMPLE with Scala 2.12 and JDK 8!https://t.co/FbvkffA6Hl

— William Narmontas (@ScalaWilliam) December 29, 2016

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