PMD has type resolution rules that depend on reflection. It's supposed to be just a matter of using auxclasspath. I've tried both with and without. The only materials I can find online imply it doesn't work out of the box. Any ideas?
The comment in the above linked blog is actually correct. I was adding the asm/jaxen jars to the wrong classpath. I had added them to the classpath of the Java process that I use to launch Ant (which is what I had always done in the past.) It needed to literally be in the classpath of the taskdef.