Question

I’m need a regular expression in Java that I can use to retrieve the domain.tld part from any url. So https://foo.com/bar, http://www.foo.com#bar, http://bar.foo.com will all return foo.com.

I wrote this regex, but it’s matching the whole url

Pattern.compile("[.]?.*[.x][a-z]{2,3}");

I’m not sure I’m matching the “.” character right. I tried “.” but I get an error from netbeans.

Update:

The tld is not limited to 2 or 3 characters, and http://www.foo.co.uk/bar should return foo.co.uk.

Answer 1

I would use the java.net.URI class to extract the host name, and then use a regex to extract the last two parts of the host uri.

import java.net.URI;
import java.net.URISyntaxException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RunIt {

    public static void main(String[] args) throws URISyntaxException {
        Pattern p = Pattern.compile(".*?([^.]+\\.[^.]+)");

        String[] urls = new String[] {
                "https://foo.com/bar",
                "http://www.foo.com#bar",
                "http://bar.foo.com"
        };

        for (String url:urls) {
            URI uri = new URI(url);
            //eg: uri.getHost() will return "www.foo.com"
            Matcher m = p.matcher(uri.getHost());
            if (m.matches()) {
                System.out.println(m.group(1));
            }
        }
    }
}

Prints:

foo.com
foo.com
foo.com