Extract host name/domain name from URL string

Question

I have a URL like http://hostname:port_no/control/login.jsp.

I have the above url stored in some String.Now, I need to extract hostname from the String.

I am doing like this in my Java code

String domain = url.substring(url.indexOf('/') + 2, url.lastIndexOf(':'));

I want to know if there is any better way to do the same.

You could try using: [URL](http://docs.oracle.com/javase/7/docs/api/java/net/URL.html) class for parsing. — Re Captcha, Apr 15 '14 at 09:11
I request you to change subject of question to 'Get extract host name/domain name from url string' please do needfull — niiraj874u, Apr 16 '14 at 04:52

score 20 · Accepted Answer · answered Apr 15 '14 at 09:17

You can use the java.net.URI-class to extract the hostname from the string.

Here below is a method from which you can extract your hostname from a string.

public String getHostName(String url) {
    URI uri = new URI(url);
    String hostname = uri.getHost();
    // to provide faultproof result, check if not null then return only hostname, without www.
    if (hostname != null) {
        return hostname.startsWith("www.") ? hostname.substring(4) : hostname;
    }
    return hostname;
}

This above gives you the hostname, and is faultproof if your hostname does start with either hostname.com/... or www.hostname.com/..., which will return with 'hostname'.

If the given url is invalid (undefined hostname), it returns with null.

+1, Using `URI` is _safer_ (and better) than using `URL` alone. — Hungry Blue Dev, Apr 15 '14 at 09:51

score 8 · Answer 2 · answered Apr 15 '14 at 09:13

8

java.net.URL aURL;
try {
    aURL = new java.net.URL("http://example.com:80/docs/");
    System.out.println("host = " + aURL.getHost()); //example.com
} catch (MalformedURLException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

answered Apr 15 '14 at 09:13

niiraj874u

2,180
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you can use this or you can use regular expressions. Look for class `Pattern` and `Matcher`. – pratikch Apr 15 '14 at 09:16

score 7 · Answer 3 · answered Apr 15 '14 at 09:12

7

java.net.URL u = new URL("http://hostname:port_no/control/login.jsp");
System.err.println(u.getHost());

answered Apr 15 '14 at 09:12

PeterMmm

24,152
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4

System.out.println()?? – akash Apr 15 '14 at 09:14
2

@MaciejCygan I believe it's an _awesome_ [troll](http://codegolf.stackexchange.com/tags/code-trolling/info). – Hungry Blue Dev Apr 15 '14 at 09:50
@ambigram_maker indeed it is ;) – Maciej Cygan Apr 15 '14 at 09:53
1

`all good but why Sys.err ??` A: It is a valid use case for the method getHost(). It is an **example**. – PeterMmm Apr 15 '14 at 09:54
Best answer. Thank you. – user674669 Jan 15 '20 at 08:12

score 1 · Answer 4 · answered Nov 20 '19 at 01:06

A solution using Regular expression and group:

    String pattern = "(\\w*://)([\\w-_.]+)([:\\w\\W]*)";
    Pattern r = Pattern.compile(pattern);
    Matcher m = r.matcher(a);
    if (m.find())
    {
        System.out.println(m.group(0));
        System.out.println(m.group(1));
        System.out.println(m.group(2));
        System.out.println(m.group(3));
    }

group(2) is the hostname.

score 0 · Answer 5 · answered Apr 15 '14 at 09:15

0

If you want string work, then try the following code sample,

String URL= "http://hostname:port_no/control/login.jsp";
String s_URL[] = ULR.split("//");
String s1 = s_URL[1];
String s2[] = s1.split(":");
String hostname = s2[0];

answered Apr 15 '14 at 09:15

astack

3,837
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score 0 · Answer 6 · answered Apr 15 '14 at 09:39

0

In Java:

String hostname = url.split("://")[1].split(":")[0];
String portnumber = url.split("://")[1].split(":")[1].split("/")[0];

Hope this helps.

answered Apr 15 '14 at 09:39

luiscosta

855
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score 0 · Answer 7 · answered Jun 04 '18 at 20:14

@KarelG's answer is the best answer, though I had specific issues with certain non-standard domains. The example issue is self contained below.

For certain "real world" input values, I had to add a check to the URI scheme to avoid mis-parsing of some addresses. This is the changed code.

import java.net.URI;
import java.net.*;

public class Domain {
    public static String getDomainName(String url) {
        try {
            URI uri = new URI(url);
            String domain = uri.getHost();
            System.out.println("domain: " + domain);
            if (uri.getScheme() != null) {
                return domain.startsWith("www.") ? domain.substring(4) : domain;
            } else {
                return uri.getSchemeSpecificPart();
            }

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

}

Below is the test case and value that was failing.

Domain.java javac Domain.java java Domain

import java.net.URI;
import java.net.*;
import java.io.*;

public class Domain {

    public static String longname = "https://www.3dprintingmedia.network/longform/page.html";
    public static String name = "www.3dprintingmedia.network";

    public static void getDomain(String url) {
        try {
                        URI uri = new URI(url);
                        String domain = uri.getHost();
            System.out.println("protocol: " + uri.getScheme());
            System.out.println("path: " + uri.getPath());
                        System.out.println("name: " + name);
                        System.out.println("domain: " + domain);
                        System.out.println(domain.startsWith("www.") ? domain.substring(4) : domain);
        } catch (Exception e) {
                        e.printStackTrace();
        }
   }

    public static void main(String[] args) {
       System.out.println("Parsing domain: " + name); 
       getDomain(longname);
       getDomain(name);
       System.exit(0);
    }
}

Extract host name/domain name from URL string

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