There is a sandbox plugin to enhance with Maven available at http://mojo.codehaus.org/openjpa-maven-plugin/usage.html.
Alternately, enhancement can be performed by using the antrun plugin to launch the command-line enhancement tool on your classes:
<build> <plugins> <plugin> <artifactId>maven-antrun-plugin</artifactId> <executions> <execution> <phase>process-classes</phase> <configuration> <tasks> <java classname="org.apache.openjpa.enhance.PCEnhancer" classpathref="maven.runtime.classpath" dir="target/classes" fork="true" /> </tasks> </configuration> <goals> <goal>run</goal> </goals> </execution> </executions> </plugin> </plugins> </build>