Add the following fragment to your pom file to execute the rmic plugin as part of the "process-classes" phase. Modify the class file(s) specified to your own classes.
<project>
...
<build>
<plugins>
<plugin>
<groupId>org.freehep</groupId>
<artifactId>freehep-rmic-plugin</artifactId>
<version>2.0-SNAPSHOT</version>
<executions>
<execution>
<goals>
<goal>generate</goal>
</goals>
<configuration>
<classes>
<class>com.yourcompany.YourClass</class>
<class>...</class>
</classes>
<keep>true</keep>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
...
</project>