I ran across the use case described in the title when working with a legacy web application which also serves as a dependency for other (plugin) projects. To this end, besides the War file which is deployed as web application, I would like to have the contained Jar file being installed separately in my local repository.
This additional artifact can be obtained with a few lines in the pom.xml:
This execution extracts the Jar file which is produced during the preparations of the War file and installs it with the project’s default group id, artifact id, and version.
-  Maven Install Plugin: install-file