The jaxen project is a Java XPath Engine. jaxen is a universal object model walker, capable of evaluating XPath expressions across multiple models. Currently supported are dom4j, JDOM, and DOM.

jaxen provides a single point for XPath expression evaluation, regardless of the target object model, whether its dom4j, JDOM, DOM, XOM, JavaBeans, or what not.

Why is jaxen better than [some other XPath technology] ?

jaxen is better than werken.xpath specifically because it better handles XPath expressions, and syntax error reporting. Additionally, since jaxen is a unified code-base, developer effort isn't split between maintaining the dom4j version and the JDOM version. More hands working on the same project reduces bug count.

jaxen may be perceived to be better than other XPath technologies since it provides a single cohesive API for evaluating XPaths against multiple object models. Learn the jaxen API, and apply it to dom4j, JDOM, XOM or DOM trees in exactly the same way.

Also, since jaxen works against an adaptor which provides InfoSet access to arbitrary object models, it should be possible to build even larger tools in terms of jaxen, to work with multiple models. For example, an XQL engine could be developed, which would automagically work with all models already supported by jaxen.