Groovy function that will follow a number of redirects to get the real URL of a webpage/service

FindRealUrl.groovy

def findRealUrl(url) {
    HttpURLConnection conn = url.openConnection()
    conn.followRedirects = false
    conn.requestMethod = 'HEAD'
    if(conn.responseCode in [301,302]) {
        if (conn.headerFields.'Location') {
          return findRealUrl(conn.headerFields.Location.first().toURL())
        } else {
            throw new RuntimeException('Failed to follow redirect')
        }
    }
    return url
}

I think you are missing a url.connect() statement before testing the responseCode.

really cool snippet! but note: a requestMethod of "GET" might in some cases be more accurate. It was in our case

numerous servers (ie amazon.com) return a 50x when given a HEAD request...

def findRealUrl(url, METHOD='HEAD') {
    HttpURLConnection conn = url.openConnection()
    conn.followRedirects = false
    conn.requestMethod = METHOD
    conn.connect()
    if(conn.responseCode in [301,302]) {
        if (conn.headerFields.'Location') {
          return findRealUrl(conn.headerFields.Location.first().toURL())
        } else {
            throw new RuntimeException('Failed to follow redirect')
        }
    }
    return url
}