@Override
    public Resource createRelative(String relativePath) {
        String pathToUse = StringUtils.applyRelativePath(this.path, relativePath);
        return (this.file != null ? new FileSystemResource(pathToUse) :
            new FileSystemResource(this.filePath.getFileSystem(), pathToUse));
    }
This implementation creates a FileSystemResource, applying the given path
relative to the path of the underlying file of this resource descriptor.

see org.springframework.util.StringUtils#applyRelativePath(String, String)
analyzer/src/main/java/nl/basjes/parse/useragent/utils/springframework/core/io/FileSystemResource.java