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Note that the class HelloWorldPartition has to be in the class path of the server. Withgout, starting the server leads to a ClassNotFoundException. You can copy the jar file which results from the build to the lib directory and adjust the command line parameters in the apacheds.sh script.
verification
After adding the HelloWorldPartition to the directory service like above (embedded or via configuration in server.xml), you can browse it with an LDAP browser like the one from Apache Directory Studio. Here are some screen shots.