How to bundle JARs of an XSLT processor to Firefox extension (XPI)

Hi there,

For a prototype I need to use a XSLT processor, which support node-set() 
in conjunction of an Firefox extension.

Therefore I want to bundle the JARs of a XSLT processor with the 
extension XPI.

Is this possible to access the classes from the JAR from the Javascript 
at all?
And if so, is there any sample code, tutorial known, where I can get a 
feeling for the solution?

Thanks in advance,
Svante