Question

My company doesn’t use Apache, so we’ve spun up our own socket code. In the following, HTMLDoc is my version of a server response. I’m trying to grab the URL that a browser would redirect to if the original URL gave a 301 response code:

    static public void main(String args[]) throws Exception
{

    String spec = "http://some_url_with_301_redirect.com";
    URL my_url = new URL(spec);

    HTMLDoc doc = getDocFromURL(my_url);

    // Do stuff with the doc.
}

public static HTMLDoc getDocFromURL(URL url)
{
    try
    {
        URLConnection u = url.openConnection();

        if ( u instanceof HttpURLConnection )
        {
            HttpURLConnection http_u = (HttpURLConnection)u;

            int response_code = http_u.getResponseCode();

            if (response_code == 300 || response_code == 301 || response_code == 302)
            {
                URL redirected_url = getRedirectedURL(url);

                return getDocFromURL(redirected_url);
            }
        }

        return null;
    }

    catch(Exception e) 
    {
        e.printStackTrace();
        return null;
    }
}

The trouble is, I have no idea what the method getRedirectedURL(url) should look like. Is there a quick call I can do to http_u that I’m not familiar with?

Answer 1

A HTTP 301 response is always accompanied by a Location header. A typical response looks looks like

HTTP/1.1 301 Moved Permanently
Location: http://www.example.org/index.asp

You can read this header and get the redirected URL. The sample code to do this is mentioned in the link posted by Jon Lin in the comments above.