The Maven team is pleased to announce the release of the Maven PMD Plugin, version 2.7.1

A Maven plugin for the PMD toolkit, that produces a report on both code rule violations and detected copy and paste
    fragments,
    as well as being able to fail the build based on these metrics.

http://maven.apache.org/plugins/maven-pmd-plugin

You should specify the version in your project's plugin configuration:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-pmd-plugin</artifactId>
  <version>2.7.1</version>
</plugin>

Release Notes - Maven PMD Plugin - Version 2.7.1

Bug
* [MPMD-142] PMD Report for maven site fails with ClassCastException

Enjoy,

-The Maven team