Calling a overloaded static java method which accepts an interface as a parameter

Hi All,

I’m trying to call with a
single parameter. The open method has two single parameter signatures,
which accepts a String, and one which accepts an interface
(org.apache.commons.configuration.Configuration). I want to call the
latter, so I’m attempting to do this using java_send:

args =
graph = com.thinkaurelius.titan.core.TitanFactory.java_send(:open, args,

I’m using java.lang.Class.for_name to populate the array used in the
parameter, because if I don’t (for example, if I instead do
args = [org.apache.commons.configuration.Configuration]
), I get “TypeError: cannot convert instance of class
to class java.lang.Class”. StackOverflow tells me “This is because java
interfaces become Ruby Modules by default and the second argument to
:java_method expects an array of Class objects” (

But here’s what happens with Class.for_name:

LoadError: load error: /Users/mccraw/Documents/RubySolstice/app/titan –

The JRuby wiki FAQ ( tells me:

"When JRuby runs at the command line, it loads into the bootstrap class
loader. This class loader lives above CLASSPATH, so libraries you add to
CLASSPATH are not normally visible. Because Class.forName uses the class
loader of the nearest non-system class that called it, it ends up seeing
JRuby as the caller and looking for classes only in CLASSPATH.

The workaround for this is simple: Uuse JRuby’s import or include_class
methods to load the class, or just reference it directly as in
Java::my.package.MyClass or org.postgresql.Driver"

This jives with something else I’ve noticed, which is that if I jar up
my ruby code into a jar whose manifest has the apache commons
jar in its classpath, the code works great. Oddly though, even if I
jruby with -I/path/to/dir/containing/commons-configuration.jar, I still
the ClassNotFoundException. Note that in the class containing this
I’m requiring the jar explicitly:
{ |jar| require jar }

So one way, the class loader can’t seem to see it, and the other way,
seems to convert it to a module. I have googled my brains out and am
out of crazy variants to try. Surely people are calling methods that
accept interfaces as parameters. Is there some standard way to handle
that I’ve missed?

Thanks so much!


As luck would have it, I was closing down the way too many browser tabs
had open, and something in one of them caught my eye which helped me
my own question. If I change the second parameter of java_send to:

[org.apache.commons.configuration.Configuration.java_class] (note the
‘java_class’ message that gets tacked on the end), everything works just

I don’t really understand how this works – if
org.apache.commons.configuration.Configuration is in fact an
org.jruby.RubyModule (printing out the results of messaging
class.namespits out merely ‘Module’), I would have expected to see a
message in the RubyModule API doc, but I don’t. I suppose jruby is
this behavior into Module elsewhere? At any rate, the code is now
and I can sleep soundly.

Sorry for the noise!


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