Find Facebook user (url to profile page) by known email address

Question

I have an email address and want to find out if there is a Facebook user linked to this address. If there is, then I want to retrieve the url to this users profile page and

Answer 1

Andreas, I've also been looking for an "email-to-id" ellegant solution and couldn't find one. However, as you said, screen scraping is not such a bad idea in this case, because emails are unique and you either get a single match or none. As long as Facebook don't change their search page drastically, the following will do the trick:

final static String USER_SEARCH_QUERY = "http://www.facebook.com/search.php?init=s:email&q=%s&type=users";
final static String USER_URL_PREFIX = "http://www.facebook.com/profile.php?id=";

public static String emailToID(String email)
{
    try
    {
        String html = getHTML(String.format(USER_SEARCH_QUERY, email));
        if (html != null)
        {
            int i = html.indexOf(USER_URL_PREFIX) + USER_URL_PREFIX.length();
            if (i > 0)
            {
                StringBuilder sb = new StringBuilder();
                char c;
                while (Character.isDigit(c = html.charAt(i++)))
                    sb.append(c);
                if (sb.length() > 0)
                    return sb.toString();
            }
        }
    } catch (Exception e)
    {
        e.printStackTrace();
    }
    return null;
}

private static String getHTML(String htmlUrl) throws MalformedURLException, IOException
{
    StringBuilder response = new StringBuilder();
    URL url = new URL(htmlUrl);
    HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
    httpConn.setRequestMethod("GET");
    if (httpConn.getResponseCode() == HttpURLConnection.HTTP_OK)
    {
        BufferedReader input = new BufferedReader(new InputStreamReader(httpConn.getInputStream()), 8192);
        String strLine = null;
        while ((strLine = input.readLine()) != null)
            response.append(strLine);
        input.close();
    }
    return (response.length() == 0) ? null : response.toString();
}