Extensions are used to enable Wagon providers, used for the transport of artifact between repositories, and plug-ins which provide lifecycle enhancements.
<project>
...
<build>
<extensions>
<extension>
<groupId>org.apache.maven.wagon</groupId>
<artifactId>wagon-ftp</artifactId>
<version>1.0-beta-2</version>
</extension>
</extensions>
</build>
...
</project>
Note: Wagon 1.0-beta-3+ requires Maven 2.1.0 or above. For Maven 2.0.10 and earlier, use Wagon 1.0-beta-2.
Note: Some Wagons require JDK 5.0 to operate correctly.
<project>
...
<build>
<plugins>
<plugin>
<groupId>org.codehaus.plexus</groupId>
<artifactId>plexus-maven-plugin</artifactId>
<version>1.1-alpha-8-SNAPSHOT</version>
<extensions>true</extensions>
<configuration>
...
</configuration>
</plugin>
</plugins>
</build>
...
</project>