Unable to locate Source XRef to link to

You should add the maven-jxr-plugin to the reportingPlugin section.

<reporting>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jxr-plugin</artifactId>
            <version>3.3.0</version>
        </plugin>
    </plugins>
</reporting>

Re run it and enjoy.

BTW, maybe you’ll need to run once the jxr:jxr goal to first generate some file that will be used by pmd.