I think the easiest option is to build/use a WAR similar to https://github.com/ModeShape/modeshape/tree/master/web/modeshape-web-cmis-war

Depending on what type of protocol you want (SOAP, REST, AtomPUB etc) the web.xml will probably be a bit different (you do need to make sure the listeners & context params are present).

So you can either use the above WAR as a Maven artifact and overlay (via the WAR plugin) your own web.xml or you can build a separate module in your project.

We've also updated our documentation: ModeShape's CMIS Service - ModeShape 4 - Project Documentation Editor and added an example: modeshape-examples/modeshape-cmis-example at master · ModeShape/modeshape-examples · GitHub which shows how to do this.

The same goes for the REST & WebDAV services.