1) I'm not sure about integrating this with Eclipse compilation, other than setting the execution to also refresh the workspace (such as for a run configuration). I only intended to provide IDE-independent code formatting during the build.
2) It appears that the maven-eclipse-plugin and m2eclipse are no longer compatible (only used separately, the m2eclipse goal was removed in 2.8).
For m2eclipse, the Eclipse settings could be committed back in the .settings svn directory (and kept in sync with the formatter xml used by the plugin, proposed in patch)
Since the following approach is not for m2eclipse, I assume it is not an option.
For Eclipse, the settings could be added when generating the project with the eclipse goal in the maven-eclipse-plugin, using a config similar to this example (uses tools module proposed in patch):
Note that the maven-eclipse-plugin currently overwrites the default core.prefs, so this resource might need to be filtered to keep the compiler version in sync (as mentioned in https://jira.codehaus.org/browse/MECLIPSE-641)