The org.apache.commons.jxpath package defines a simple interpreter of an expression language called XPath. JXPath applies XPath expressions to graphs of objects of all kinds: JavaBeans, Maps, Servlet contexts, DOM etc, including mixtures thereof.
JXPath home page:
http://commons.apache.org/jxpath/
Articles
Java object queries using JXPath - Bart van Riel, JavaWorld, March 2007
JXPath Tutorial by Bart van Riel
Release Plans
JXPath Release Plan 1.2: JXPathRelease1.2