how to handle structured data from Java

I need to pass an attribute value to a Java method implemented by a
co-worker and save the resulting object in a variable (since it's a
relatively expensive operation), then access the object's string
components.  Should I write an extension function in Java to call his
method and convert the object into a DOM Node that would be stored via
<xsl:value-of name="variable" select="extension:function(@attribute)">?
How would I then access its subnodes -- via select="$variable/component-x"?

Or is there a better way?  I'm using Xalan, but would like to implement
this in as portable a fashion as possible -- will EXSLT help?

Thanks,
-- 
Kevin