ClassUseSample.java

package play;

import org.jruby.embed.PathType;
import org.jruby.embed.ScriptingContainer;

public class ClassUseSample {
	public ScriptingContainer container;
	public String file;
	
    public ClassUseSample(String filename) {
		file = filename;
        System.out.println("[" + getClass().getName() + "]");
        container = new ScriptingContainer();
        container.runScriptlet(PathType.CLASSPATH, file);
    }

	public RubyObject rubyClass(String classname) {
		Object obj = container.runScriptlet(classname);
		return new RubyObject(obj);
	}

	public RubyObject newRubyObject(String classname, Object[] args) {
		RubyObject rc = rubyClass(classname);
		Object robj = rc.send("new", args, Object.class);
		return new RubyObject(robj);
	}
	
	public class RubyObject {
		private Object obj;
		
		public RubyObject(Object object) {
			obj = object;
		}
		
		public <T> T send(String methodName, Class<T> returnType) {
	        return container.callMethod(obj, methodName, returnType);
	    }
	
		public <T> T send(String methodName, Object singleArg, Class<T> returnType) {
	        return container.callMethod(obj, methodName, singleArg, returnType);
	    }
	
		public <T> T send(String methodName, Object[] args, Class<T> returnType) {
	        return container.callMethod(obj, methodName, args, returnType);
	    }
	}

    public static void main(String[] args) {
       	ClassUseSample ruby = new ClassUseSample("tree.rb");

		Object[] call_args = {"pink", "March-April"};
		RubyObject flower = ruby.newRubyObject("Flower", call_args);
		System.out.println(flower.send("color", String.class));
    }
}

tree.rb

class Tree
  attr_reader :name, :shape, :flower
  def initialize(name, shape, flower)
    @name, @shape, @flower = name, shape, flower
  end
  def to_s
    "#{name.capitalize} is a #{shape} shaped tree, and blooms #{flower.color} flowers in #{flower.bloomtime}."
  end
  def update(color, bloomtime)
    flower.color = color
    flower.bloomtime = bloomtime
  end
end

class Flower
  attr_accessor :color, :bloomtime
  def initialize(color, bloomtime)
    @color, @bloomtime = color, bloomtime
  end
end