How can I customize the location of the datastore file while working with GAE/J.
The option --datastore_path doesn't seem to work with GAE/J.
And if it is possible, what option do I use in the maven-gae-plugin.
I assume you mean while running the dev app server locally. Try the --generated_dir option with <sdk>/bin/dev_appserver.sh:
--generated_dir=dir Set the directory where generated files are created.
The generated files include the local datastore file.