This also works with maven by defining the resources tag. You can name your src folder names whatever you like.
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.java</include>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
</resource>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.java</include>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
</resource>
<resource>
<directory>src/main/generated</directory>
<includes>
<include>**/*.java</include>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
</resource>
</resources>