How does one perform an ad-hoc reactor build over multiple maven projects without a root project?
This used to be possible in maven2 by invoking the mvn command with the '-r' option which would search recursively from the working directory for projects and organize them in the reactor to build in the correct order even if the projects did not share a common parent pom.xml. Optionally one could specifically include or exclude certain projects using maven.reactor.includes and maven.reactor.excludes option.
I realize that the legacy reactor mode was removed from maven3 but I can't figure out how to achieve this functionality using the 'make-like' reactor mode.
The "Maven 2"-style reactor feature has been removed following this discussion on the mailing list. The relevant JIRA issue is MNG-4260.
As mentioned in the comments above, it's best to create a top-level pom with a <modules> section that lists the directories containing projects. (If you don't always build all of your projects at the same time, you can put separate modules sections in profiles).
来源：https://stackoverflow.com/questions/5751561/how-do-you-perform-a-reactor-build-in-maven3-without-a-root-project