Apache Jackrabbit and basic Java interfacing

I'm building a content management system (isn't everyone?) and it looks 
like using Apache Jackrabbit <http://jackrabbit.apache.org/> for a lot 
of the backend would save a lot of work and give me a pretty powerful 
platform to work from.

Anyone tried making this work with Helma? I would happily compose an 
honorary poem to anyone who could share working code.

More basic: I'm still trying to get to where I can instantiate a given 
Java class in Helma. I have successfully done built-in Java classes, but 
I haven't been able to instantiate any from JARs yet. I'm sure it's 
because I'm missing some critical and obvious step. I've tried putting 
the jars in lib/ext, and Helma says its adding them to the classpath 
when it starts up, but I don't seem to be accessing anything real via 
Packages.org.apache.jackrabbit...

I apologize for the trivial nature of my problems. A few months from now 
when I'm a Helma guru ( :-) ), I'll help answer newbie questions, too.