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How to obtain hostname during servlet init

Bear Bibeault
Author and ninkuma

Joined: Jan 10, 2002
Posts: 60782

I'd like to obtain the host name of the server my web app is running on during the init() method of one of my servlets (without resorting to init params or system properties which could speak with false tongue).
Any clues? There doesn't seem to be any way to get this info from the servlet config or servlet context.
You can get this from a request (using getServerName()) but the init() method is, of course, called long before any requests are made.
Seems like this is certainly something that should be able to be determined, but I can't seem to find a way.
Any clues would be most appreciated!

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Dave Landers
Ranch Hand

Joined: Jul 24, 2002
Posts: 401
I think the problem is that a host doesn't necessarily know its name - especially if its behind a firewall or router or load balancer or edge caching technology or whatever.
It can know its own name, but that name may have nothing to do with how a client browser would address it.
For example, I can do a ping of www.yahoo.com and get something like this (some stuff deleted):
$ ping www.yahoo.com
PING www.yahoo.akadns.net ( ...
64 bytes from w2.scd.yahoo.com ( ...
64 bytes from w2.scd.yahoo.com ( ...
Now if you were coding the yahoo server, which host name would you want: www.yahoo.com, www.yahoo.akadns.net, or w2.scd.yahoo.com or any of the who knows how many others that are out there serving yahoo content?
And maybe you have one server hosting requests from several different names.
So maybe lazily initialize it off the first request. Hopefully that request is not going to be an admin testing with http://localhost/ So maybe its even better to query each request for "how did you get here" information.
Anyway, back to your question, if you still want the host name, how about
or .getCanonicalHostName() (JDK 1.4).
Bear Bibeault
Author and ninkuma

Joined: Jan 10, 2002
Posts: 60782

Hey Dave,
Thanks for the info. I decided to go with the lazy initialization scheme. Probably better for startup performance, anyways.
thanks again!
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subject: How to obtain hostname during servlet init
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