How can I retrieve the sub domain in a servlet? Does spring have any helpers

Question

I first want to know if there is a built-in way of getting a subdomain from a url using pure servlets?

And then if spring has any helpers?

So my urls would be like:

jonskeet.stackoverflow.com

Where JonSkeet is the subdomain.

I will create a filter that will load a object based on the subdomain value.

BTW, when creating a filter, is there a way to order the filters to make sure they all fire in a specific order?

+1 if you wondered if SO has really created a Jon Skeet sub-domain and tried to visit http://jonskeet.stackoverflow.com — Kiril, Mar 21 '12 at 20:33
No, I don't think you can go further than obtaining the URL and then splitting the String yourself. BTW, you should not put more than one question, particularly when your question about filters can be answered quickly with a Google search. — madth3, Mar 21 '12 at 20:34
wow that is surprising, I was certain there would be something. — Blankman, Mar 21 '12 at 20:36

score 8 · Answer 1 · answered Mar 21 '12 at 20:40

8

I doubt there is a special API for this. But you can get it from HttpRequest using request.getServerName().split("\\.")[0]. It seems it is easy enough.

Limitation is that you cannot support "subdomain" that contains dot characters, e.g. jon.skeet.stackoverflow.com.

answered Mar 21 '12 at 20:40

AlexR

114,158
16
130
208

Ah, sub-domains cannot **really** contain dots, see for more details: http://stackoverflow.com/questions/7111881/what-are-the-allowed-characters-in-a-sub-domain – Kiril Mar 21 '12 at 20:43
In other word: the dot is not part of the sub-domain, it's a separator for the textual portions of the domain name. – Kiril Mar 21 '12 at 20:58
1

getServerName() returns also www, so it will fail, sooner or later – Dawid D Mar 18 '14 at 01:46
But for practical purposes, "www" is also a subdomain. – Renascienza Jun 01 '16 at 16:29
@Renascienza, FYI, not all domains start with 'www' – AlexR Jun 02 '16 at 17:30
@AlexR, of course not. But "www" is a *valid* subdomain. – Renascienza Jun 03 '16 at 01:25

score 1 · Answer 2 · answered Jun 01 '16 at 17:06

Use Guava.

Gradle:

dependencies {
 compile group: 'com.google.guava', name: 'guava', version: '19.0'
 ...
}

Java:

    private String getSubdomain(HttpServletRequest req) {

        String site = req.getServerName();

        String domain = InternetDomainName.from(site).topPrivateDomain().toString();
        String subDomain = site.replaceAll(domain, "");
        subDomain = subDomain.substring(0, subDomain.length() - 1);

        return subDomain;
}

So, "jon.skeet.stackoverflow.com" will return "jon.skeet".

How can I retrieve the sub domain in a servlet? Does spring have any helpers

2 Answers2