How do you clear Apache Maven's cache?

Recently, Apache Maven seems to be having caching issues. Performing clean installs on our projects using Windows Vista or Windows 7 sometimes produce artifacts with the same data as a previous build even though the newer artifact's files should have been updated.

Is there any way to clear this cache to force maven to always trigger a clean build of the local artifact that should be built?

In particular, we're having issues building a webapp with the war plugin. Maven version is 3.0.3. War plugin version is 2.1.1.

Solution 1:

Delete the artifacts (or the full local repo) from c:\Users\<username>\.m2\repository by hand.

Solution 2:

To clean the local cache try using the dependency plug-in.

1. mvn dependency:purge-local-repository: This is an attempt to delete the local repository files but it always goes and fills up the local repository after things have been removed.
2. mvn dependency:purge-local-repository -DreResolve=false: This avoids the re-resolving of the dependencies but seems to still go to the network at times.
3. mvn dependency:purge-local-repository -DactTransitively=false -DreResolve=false: This was added by Paweł Prażak and seems to work well. I'd use the third if you want the local repo emptied, and the first if you just want to throw out the local repo and get the dependencies again.

Solution 3:

Have you checked/changed the updatePolicy settings for your repositories in your settings.xml.

This element specifies how often updates should attempt to occur. Maven will compare the local POM's timestamp (stored in a repository's maven-metadata file) to the remote. The choices are: always, daily (default), interval:X (where X is an integer in minutes) or never.

Try to set it to always.