assertArgumentNotNull("rootDir", rootDir);
        assertArgumentNotNull("handler", handler);

        final File baseDir = getBaseDir(rootDir, baseDirectory);
        if (baseDir.exists()) {
            traverseFileSystem(rootDir, baseDir, handler);
        }
    }

    /**
     * Traverses resources contained in a Jar file.
     *

    protected static final ConcurrentMap<String, TraverserFactory> traverserFactories = newConcurrentHashMap();
    static {
        addTraverserFactory("file", (url, rootPackage, rootDir) -> new FileSystemTraverser(getBaseDir(url, rootDir), rootPackage, rootDir));
        addTraverserFactory("jar", JarFileTraverser::new);
        addTraverserFactory("zip", (url, rootPackage,