In maven how can I include non-java src files in the same place in the output jar?

You could add the following in your pom indicating that the resources are available in src/main/java and including the type of resources.

<build>
    <resources>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.properties</include>
            </includes>
        </resource>
    </resources>
</build>