Getting server name during servlet initialization

Question

I know the request object has a function to get the server name. (i.e. HttpServletRequest.getServerName() )

What if I need the same functionality inside the initialization of a servlet? How do I do this?

Are there any problems/issues if I invoke java.net.InetAddress.getLocalHost().getCanonicalHostName() to get the server name? — Aleks Felipe
– Aleks Felipe, Commented Nov 4, 2010 at 23:44
yes, when you have alias names for your host. For example your application may be visible under http://www.google.com/ while using getCanonicalHostName() may give you http://nuq05s02-in-f18.1e100.net/ — Andre Holzner
– Andre Holzner, Commented Feb 27, 2015 at 16:18

BalusC · Accepted Answer · 2010-11-04 22:38:08Z

4

This information is request based and not strictly application based. It can namely change per request. All you have at hands during servlet initialization is the ServletContext instance which in turn offers methods like getInitParameter(). You could make use of it to access application wide settings.

So your best bet is to manually set the server name as a context parameter in web.xml

<context-param>
    <param-name>serverName</param-name>
    <param-value>foo</param-value>
<context-param>

so that you can obtain it as follows in servlet's init() method:

String serverName = getServletContext().getInitParameter("serverName");

Another (not recommended) alternative is to set it as display name in web.xml

<display-name>foo</display-name>

so that you can obtain it as follows:

String serverName = getServletContext().getServletContextName();

edited Nov 4, 2010 at 22:38

answered Nov 4, 2010 at 22:22

BalusC

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Comments

Bozho · Accepted Answer · 2010-11-05 08:08:29Z

3

If for some reason you don't want to use BalusC's answer, and you don't need the name immediately, you can do it lazily. The other day I implemented a similar scenario that way:

private volatile boolean initialized;

public void doGet(..) {
    if (!initialized) {
       synchronized(this) {
          if (!initialized) {
              initialize(request.getServerName())
          }
       }
    }
}

(The double-checked locking for lazy-initialization may be implemented in multiple ways. See wikipedia)

edited Nov 5, 2010 at 8:08

answered Nov 4, 2010 at 22:36

Bozho

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Peter · Accepted Answer · 2016-05-06 12:10:29Z

1

InetAddress.getLocalHost().getHostName()

answered May 6, 2016 at 12:10

Peter

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MForster · Accepted Answer · 2010-11-04 21:57:50Z

0

I think that's not possible. A host can have multiple names. Which one should be returned? And the host might not even know about all names that are configured in DNS.

answered Nov 4, 2010 at 21:57

MForster

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2 Comments

Nic Cottrell Over a year ago

I think the asker wants to get the same value as from HttpServletRequest.getServerName() but from a generic HttpServlet. There is standard behaviour for which name to return.

MForster Over a year ago

The HttpServletRequest does contain a server name because the web browser sends one. On initialization of the servlet there is no request around to read the server name from.

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