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GlassFish build depends on properly functioning several custom lifecycle mappings and artifact handlers. Because these are necessary to resolve dependencies and to run "gf:run" goal and etc., it is critical that these extensions be made available to Maven early on during Maven execution. This definition was originally in maven-glassfish-plugin, which was integrated into Maven POM through <plugin>/<extensions>true marking, but after a series of debugging to resolve artifact resolution failure problems, it turns out that that doesn't cause Maven to load components early enough. I tried to circumbent the prolem by also registering the maven-glassfish-plugin as an extension module (via <build>/<extensions/<extension>), but that apparently confuses Maven to no end --- I get build errors like this: [INFO] Internal error in the plugin manager executing goal 'org.apache.maven.plugins:maven-jar-plugin:2.1:jar': Unable to find the mojo 'org.apache.maven.plugins:maven-jar-plugin:2.1:jar' in the plugin 'org.apache.maven.plugins:maven-jar-plugin' This is obviously one of the problematic areas of Maven, so to avoid doing hack over hack, I'm simply moving the component definitions to its own module.