to your maven plugin section in your pom.xml file. Example of the one I use below.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.6</version>
<configuration>
<warName>cas</warName>
<failOnMissingWebXml>false</failOnMissingWebXml>
<recompressZippedFiles>false</recompressZippedFiles>
<archive>
<compress>false</compress>
<manifestFile>${project.build.directory}/war/work/org.apereo.cas/cas-server-webapp/META-INF/MANIFEST.MF
</manifestFile>
</archive>
<overlays>
<overlay>
<groupId>org.apereo.cas</groupId>
<artifactId>cas-server-webapp</artifactId>
</overlay>
</overlays>
<packagingExcludes>WEB-INF/lib/tomcat-*.jar</packagingExcludes>
</configuration>
</plugin>