Ok, the default maven jar plugin adds lots of junk to the created jar file like META-INF/maven/pom.xml etc (reasoning: jar files are self describing about the maven versioning or something like that)
You will need to define:
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.1</version>
<configuration>
<archive>
<addMavenDescriptor>false</addMavenDescriptor>
</archive>
</configuration>
</plugin>
</plugins>
in your build element in the pom.xml, to have your generated jar files free from maven metadata.
http://maven.apache.org/guides/mini/guide-archive-configuration.html
