gistfile1.txt

ruby_thing.rb:

require 'jruby/core_ext'
puts "hello from ruby"

class RubyThing
  include org.test.RubyInit::RubyThingInterface

  def setJt(java_thing)
    puts "setJt"
    java_thing.say(self)
  end
end

RubyThing.add_method_signature 'setJt', [java.lang.Void::TYPE, org.test.JavaThing]
RubyThing.become_java!
org.test.RubyInit.rubyThing = RubyThing.java_class






JavaThing.java:

package org.test;

public class JavaThing {

    public JavaThing() {
    }

    public void say(RubyInit.RubyThingInterface o) {
        System.out.println("got passed: " + o);
    }
}





RubyInit.java:

package org.test;

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


public class RubyInit {

    public static interface RubyThingInterface {
        void setJt(JavaThing jt);
    }

    public static Class<? extends RubyThingInterface> rubyThing;

    public static void init() throws Exception {
        ScriptEngineManager factory = new ScriptEngineManager();
        ScriptEngine engine = factory.getEngineByName("jruby");
        FileReader reader = new FileReader("ruby_thing.rb");
        try {
            engine.eval(reader);
        } catch (ScriptException exception) {
          exception.printStackTrace();
        }
    }

    public static void main(String...args) throws Exception {
        init();
        JavaThing javaThing = new JavaThing();
        RubyThingInterface rt = rubyThing.newInstance();
        rt.setJt(javaThing);
    }
}





output:
$ java -cp .:./jruby.jar org.test.RubyInit
hello from ruby
setJt
got passed: null