Add the following fragment to your pom file to execute the aid plugin as part of the "generate-sources" phase.
<project>
...
<build>
<plugins>
<plugin>
<groupId>org.freehep</groupId>
<artifactId>freehep-aid-plugin</artifactId>
<version>2.0-SNAPSHOT</version>
<executions>
<execution>
<goals>
<goal>generate</goal>
</goals>
<configuration>
<targetDirectory>${basedir}/src/main/java</targetDirectory>
<timestampDirectory>${project.build.directory}/generated-sources/aid</timestampDirectory>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
...
</project>