How do you clear Apache Maven's cache?

Question

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.

Answer 1

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

Answer 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.

Answer 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.

Answer 4

I would do the following:

mvn dependency:purge-local-repository -DactTransitively=false -DreResolve=false --fail-at-end

The flags tell maven not to try to resolve dependencies or hit the network. Delete what you see locally.

And for good measure, ignore errors (--fail-at-end) till the very end. This is sometimes useful for projects that have a somewhat messed up set of dependencies or rely on a somewhat messed up internal repository (it happens.)

Answer 5

This works on the Spring Tool Suite v 3.1.0.RELEASE, but I'm guessing it's also available on Eclipse as well.

After deleting the artifacts by hand (as stated by palacsint above) in the /username/.m2 directory, re-index the files by doing the following:

Go to:

• Windows->Preferences->Maven->User Settings menu.

Click the Reindex button next to the Local Repository text box. Click "Apply" then "OK" and you're done.

Answer 6

Use mvn dependency:purge-local-repository -DactTransitively=false -Dskip=true if you have maven plugins as one of the modules. Otherwise Maven will try to recompile them, thus downloading the dependencies again.

Answer 7

As some answers have pointed out, sometimes you really want to delete the local repository entirely, for example, there might be some artifacts that can't be purged as they are not anymore referenced by the pom.

If you want to have this deletion embedded in a maven phase, as for example clean you can use the maven-clean-plugin and access the repository through the settings, for example:

 <plugin>
    <inherited>false</inherited>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-antrun-plugin</artifactId>
    <version>1.1</version>
    <executions>
        <execution>
            <phase>clean</phase>
            <goals>
                <goal>run</goal>
            </goals>
            <configuration>
                <tasks>
                    <echo>Base clean is attached to deleting local maven cache</echo>
                    <echo>${settings.localRepository}</echo>
                </tasks>
            </configuration>
        </execution>
    </executions>
</plugin>

<plugin>
    <inherited>false</inherited>
    <artifactId>maven-clean-plugin</artifactId>
    <version>3.1.0</version>
    <configuration>
        <filesets>
            <fileset>
                <directory>${settings.localRepository}</directory>
            </fileset>
        </filesets>
    </configuration>
</plugin>

Answer 8

I've had this same problem, and I wrote a one-liner in shell to do it.

rm -rf $(mvn help:evaluate -Dexpression=settings.localRepository\
                       -Dorg.slf4j.simpleLogger.defaultLogLevel=WARN -B \
                       -Dorg.slf4j.simpleLogger.log.org.apache.maven.cli.transfer.Slf4jMavenTransferListener=warn | grep -vF '[INFO]')/*

I did it as a one-liner because I wanted to have a Jenkins-project to simply run this whenever I needed, so I wouldn't have to log on to stuff, etc. If you allow yourself a shell-script for it, you can write it cleaner:

#!/usr/bin/env bash
REPOSITORY=$(mvn help:evaluate \
  -Dexpression=settings.localRepository \
  -Dorg.slf4j.simpleLogger.defaultLogLevel=WARN \
  -Dorg.slf4j.simpleLogger.log.org.apache.maven.cli.transfer.Slf4jMavenTransferListener=warn \
  --batch-mode \
  | grep -vF '[INFO]')

rm -rf $REPOSITORY/*

Should work, but I have not tested all of that script. (I've tested the first command, but not the whole script.) This approach has the downside of running a large complicated command first. It is idempotent, so you can test it out for yourself. The deletion is its own command afterwards, and this lets you try it all out and check that it does what you think it does, because you shouldn't trust deletion commands without verification. However, it is smart for one good reason: It's portable. It respects your settings.xml file. If you're running this command, and tell maven to use a specific xml file (the -s or --settings argument), this will still work. So you don't have to fiddle with making sure everything is the same everywhere.

It's a bit wieldy, but it's a decent way of doing business, IMO.

Answer 9

So there are some commands which you can use for cleaning

 1. mvn clean cache   
 2. mvn clean install 
 3. mvn clean install -Pclean-database

also deleting repository folder from .m2 can help.