output.txt

java_class: class org.jruby.proxy.spike.Spike$Proxy0
java_class: class org.jruby.proxy.spike.Spike$Proxy0
Foo.java_class: spike.Spike
Foo.java_class.respond_to?(:isAssignableFrom): false
java_class.respond_to?(:<=): false
java_class.respond_to?(:isAssignableFrom): true
java_class == Foo.java_class: false

Spike.java

package spike;

import org.jruby.embed.ScriptingContainer;

public class Spike {


	public void inspectClass(Class cls) {
		System.out.println("java_class: " + cls);
	}


	public void doInspection(Spike inspected) {
		inspectClass(inspected.getClass());
		inspected.inspectClass(inspected.getClass());
	}

	public static void main(String[] args) {
		ScriptingContainer ruby = new ScriptingContainer();
		ruby.getVarMap().put("spike", new Spike());
		ruby.runScriptlet(Spike.class.getResourceAsStream("spike.rb"), "spike.rb");
	}
}

spike.rb

# Given a java class that could be a proxy class instance, how can you
# a) find the actual ruby class that it is a proxy for so that
# b) you can compare it to see if it contains another ruby class/module
#    in it's list of ancestors
# basically what I'd like to do is evaluate
#    java_class <= Foo
# or
#    java_class <= Java::Spike::Spike
#
# but I just can't seem to find a way to compare them :-/

class Foo < Java::Spike::Spike

  def inspectClass(java_class)
    puts "java_class: #{java_class}"
    puts "Foo.java_class: #{Foo.java_class}"
    puts "Foo.java_class.respond_to?(:isAssignableFrom): #{Foo.java_class.respond_to?(:isAssignableFrom)}"
    puts "java_class.respond_to?(:<=): #{java_class.respond_to?(:<=)}"
    puts "java_class.respond_to?(:isAssignableFrom): #{java_class.respond_to?(:isAssignableFrom)}"
    puts "java_class == Foo.java_class: #{java_class == Foo.java_class}"

  end

end

foo = Foo.new
spike.doInspection(foo)