A quick usage sample of the JSR-223 Script interface API

build.gradle

apply plugin: 'application'

mainClassName = 'foo.RubyFoo'

dependencies {
  runtime files('~/.rvm/rubies/jruby-1.7.12/lib/jruby.jar')
}

foo.rb

DEFAULT_GREETING = 'Hello'

class Greeter
  def greet name='World'
    "#{@greeting}, #{name}!"
  end

  private
  def initialize greeting=DEFAULT_GREETING
    @greeting = greeting
  end
end

DEFAULT_GREETER = Greeter.new

def default_greeting
  DEFAULT_GREETER.greet
end

Greeter.java

package foo;


public interface Greeter {
  String greet();
  String greet(String name);
  String defaultGreeting();
}

RubyFoo.java

package foo;

import java.io.*;
import javax.script.*;


public class RubyFoo {
  public static void main(String[] arg) {
    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByExtension("rb");

    try {
      engine.eval(script("/foo.rb"));

      Invocable invoker = (Invocable)engine;
      System.out.println(invoker.invokeFunction("default_greeting"));
      System.out.println(invoker.invokeMethod(engine.eval("DEFAULT_GREETER"), "greet", "Me"));

      Greeter greeter = invoker.getInterface(Greeter.class);
      System.out.println(greeter.defaultGreeting());

      Greeter indian = invoker.getInterface(engine.eval("Greeter.new 'Namaste'"), Greeter.class);
      System.out.println(indian.greet());
      System.out.println(indian.greet("Bandhu"));
    } catch (ScriptException x) {
      System.out.println("Could not execute script.\n" + x);
    } catch (NoSuchMethodException x) {
      System.out.println("Could not find function/method");
    }
  }

  private static Reader script(String path) {
    return new InputStreamReader(RubyFoo.class.getResourceAsStream(path));
  }
}