Custom Maven plugin: How to process FileSet?

I am developing my custom maven plugin. One of the parameters this plugin shall receive is a fileset. Here's a snippet from the plugin itself:

@Parameter
private FileSet[] filesets;

It compiles well and performs some of the tasks it is intended to. I can also see that the filesets field gets populated when I place such stuff into the pom:

<configuration>
    ...
    <filesets>
        <fileset dir="/">
            <include name="**/*.*"/>
        </fileset>
    </filesets>
</configuration>

But in the plugin I do not know how to iterate over the included files. The below code always gives me an empty list:

FileSetManager fileSetManager = new FileSetManager();
fileSetManager.getIncludedFiles(fileset);

Frustrated, I changed my pattern to include all files from the filesystem - but still no success. And the documentation on that topic is just about defining parameters and does not detail how to use them: https://maven.apache.org/guides/plugin/guide-java-plugin-development.html#Parameters

So how can I correctly iterate over the files in a fileset?

edit: If someone believes I gave vague information - it is as much as you can see in the Maven Plugin Development Guide. Seems there are people who can make sense of it.

Solution

I found some additional documentation specifically for handling filesets in Maven: https://maven.apache.org/shared/file-management/examples/mojo.html

While this confirms I am on the correct path however still no files are included in the fileset. I drilled this down to the configuration. It needs to look like this:

<configuration>
    ...
    <filesets>
        <fileset>
            <directory>/</directory>
            <include name="**/*.*"/>
        </fileset>
    </filesets>
</configuration>

Mind the directory element!