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From Daniel Rall <>
Subject Re: Emulating JServ's session.topleveldomain with Catalina
Date Thu, 29 Nov 2001 21:33:17 GMT
"Craig R. McClanahan" <> writes:

> On Sat, 24 Nov 2001, Daniel Rall wrote:
>> "Craig R. McClanahan" <> writes:
>> > On Wed, 21 Nov 2001, Daniel Rall wrote:
>> >
>> >> Using Tomcat 4.0.1, is there any way to emulate JServ's
>> >> session.topleveldomain context configuration?
>> >>
>> >> # Set the domain= header that gets sent with the cookie. This is
>> >> # entirely optional
>> >> # Default: null
>> >> # this is needed when we vhost to avoid multiple login
>> >>
>> >>
>> >> I would like all requests to the set of virtual hosts represented by
>> >> the glob * to share the same session ID.
>> >
>> > Unfortunately, implementing this functionality would violate the Servlet
>> > spec's requirements about sessions being scoped to a single
>> > ServletContext.  Even if you were willing to do this, you're going to run
>> > into lots of technical problems due to the fact that each webapp is loaded
>> > by it's own classloader -- trying to access a session attribute loaded
>> > from a different webapp will throw ClassNotFoundException errors at you.
>> I wasn't clear enough in my original query --  I don't want to scope
>> one session to multiple contexts, but to a single context accessed by
>> multiple host names which correspond to the same physical host (the
>> default host in server.xml).
> This is still illegal based on the same rule - each virtual host has its
> own set of webapps.  Tomcat 4 is built on this assumption.

Using the distinction you mention below, the host name used in the
request is merely a host alias (rather than a virtual host).

> One way to work around it (with Tomcat 4) would be to use the "host
> aliasing" capability, where you say that a set of host names really refer
> to the same virtual host.  This was primarily intended to deal with cases
> like "" and "" resolving to the same app, but
> could actually be used for more than that.  Check out the <Alias>
> directive (in server.xml).

Thanks for suggesting a work around, Craig (I'm only concerned with
Tomcat 4 ATM =).

Reviewing the implementation of the <Alias> directive in
StandardEngineMapper and FastEngineMapper, it appears that only
literal mappings are provided for (i.e. wildcards are not allowed

I have a requirement of supporting addition of host alias mappings at
run-time, but neither see a way to reload server.xml nor have much of
a desire to modify it from servlet code.  Is there another way to
handle this situation?  If not, would the Catalina developers be
amenable to a patch which adds wildcard capability to the host alias
feature?  Would regex or file system-style globs be preferred (I lean
towards the latter)?  If this is undesirable, what are my options
(i.e. can I configure my Engine entry in server.xml to use a custom

                            Thanks, Daniel

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