A simple Groovy script to get the final URL of a URL by hitting that URL and checking for 301, 302 response codes

getFinalURL.groovy

URL getFinalURL(String url) {
    getFinalURL(new URL(url))
}

URL getFinalURL(URL url) {
    HttpURLConnection connection = (HttpURLConnection) url.openConnection()
    connection.setInstanceFollowRedirects(false)
    connection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.94 Safari/537.36")
    connection.addRequestProperty("Accept-Language", "en-US,en;q=0.8")
    connection.addRequestProperty("Referer", "http://example.com/")
    connection.connect()

    int responseCode = connection.getResponseCode()
    if (responseCode == HttpURLConnection.HTTP_SEE_OTHER || responseCode == HttpURLConnection.HTTP_MOVED_PERM || responseCode == HttpURLConnection.HTTP_MOVED_TEMP) {
        String locationHeader = connection.getHeaderField("Location")

        if (locationHeader.startsWith("/")) {
            locationHeader = url.getProtocol() + "://" + url.getHost() + locationHeader
        }

        return getFinalURL(new URL(locationHeader))
    }

    return url
}