The Google App Engine documentation for modules (https://cloud.google.com/appengine/docs/java/modules/#Java_Configuration) describes a few .xml files. Is there a way to generate all of these files with Maven?
Some of the files seem like they have to be manually created, particularly appengine-application.xml and application.xml. Is that true or can I use Maven somehow?
No. But see this to create an AppEngine project with Maven
It explains how to use the App Engine-provided Maven App Engine artifact called appengine-skeleton-archetype to create a new project.
Then, configure your application using the generated file called src/main/webapp/WEB-INF/appengine-web.xml
Full documentation on using Maven is at Using Apache Maven which has a better link to Configuring appengine-web.xml
To generate the files with Maven, see this blog on the process Note: it appears the archetypes at the Maven Central repo have been updated to 2.0.0-1.9.10, so the part of the archetype being outdate can be ignored.
To install a project that already has appengine-application.xml or application.xml files created, see this sample as a template Look for them under:
appengine-modules-sample-java / appengine-modules-ear / src / main / application / META-INF