I think your best bet is described here. This idea is to create an in-project repository. Do this:
Package the class files into a jar. Choose an artifactid and version like so: my-classes-1.0.0.jar
Place the jar like so {project.dir}/libs/my-groupid/my-classes/1.0.0/my-classes-1.0.0.jar (the groupid and artifactid and version can be anything you like).
Add the in-project repository to your pom like so (name and id can be anything):
<!– In Project repository –>
<repository>
<id>in-project</id>
<name>In Project Repo</name>
<url>file://${project.basedir}/libs</url>
</repository>
Reference the classes like any other dependency:
<dependency>
<groupId>my-groupid</groupId>
<artifactId>my-classes</artifactId>
<version>1.0.0</version>
</dependency>