>
> It can't be turned off. In the future we may make it possible to have
> several loader repositories with a parent-child relationship
> which would
> let you have several versions of a class at once. However it
> is not yet
> clear this is cost-effective compared to running several
> jboss instances.
>
> The point of having the unified classloaders is that you can
> redeploy parts
> of your application without taking down the server, and still
> all calls are
> optimized. For instance, this lets you split very large
> applications into
> many ears that can be deployed independently yet have optimized calls
> between ejbs in different ears. You can remove and redeploy
> any of the
> ears with different classes without stopping the server.
>
> Why would you want to have several versions of a class
> deployed at once?
> Is this a real use case?
Certainly. What if I have two versions of [a part of] my website up, both
accessible via port 80, but accessed via different context roots?
Perhaps it's my perception of what an application server is. I've always
thought of an application server as a relatively heavyweight object that is
capable of hosting multiple applications. From what I'm hearing, this means
JBoss3 essentially becomes a wrapper for a single application, because in
the general case you don't know or care if two different applications have
different versions of the same classname.
I've also always thought of an .ear as a completely standalone entity.
Though I've never used them, it was my perception that the purpose of a .sar
was to partition classes within an .ear into hotdeployable units. Again,
I've never looked much into them, and I'm still using 2.4.4.
Unless the port configuration / port allocation is totally different in
JBoss3, I would envision configuring and running multiple JBoss instances on
the same machine to be somewhat cumbersome and error prone.
Anyhow, I've just always thought of two ear's as always being siblings in
the classloader tree. It seems relatively natural to envision two
[trivially] different implementations of ${whatever is the container for the
ear}, one that allows visibility between all ear's deployed in the directory
configured for that container, and another that places each ear in its own
namespace.
Either way, JBoss is still the best thing since sliced bread.
Paul
>
> david jencks
>
> >
> > Thanks,
> > Paul
> >
> > > -----Original Message-----
> > > From: David Jencks [mailto:[EMAIL PROTECTED]]
> > > Sent: Thursday, May 16, 2002 4:43 PM
> > > To: [EMAIL PROTECTED]
> > > Subject: Re: [JBoss-user] Does JBoss3 have Problems
> Deploying Similar
> > > ejb-jars in Different EARs
> > >
> > >
> > > On 2002.05.16 19:05:43 -0400 Hunter Hillegas wrote:
> > > > Whoah... Really?
> > >
> > > yup
> > > >
> > > > So I can't have two ejb-jars with classes that are named
> > > the same, in
> > > > different ears?
> > > >
> > > > Hmmmm...
> > > >
> > > > We have a content management system with EJBs that we need
> > > to deploy in
> > > > several different customer instance EARs. Are you saying we
> > > can't do that
> > > > without changing the classnames or packaging?
> > > >
> > > > For some reason I thought that each deployed EAR had its
> > > own namespace
> > > > and
> > > > you could do this...
> > > >
> > > > Did I misunderstand you?
> > >
> > > nope.
> > >
> > > You can have lots of copies of the same ejb class deployed
> > > under different
> > > ejb name and jndi names. Just be sure to only deploy one
> copy of the
> > > class. You might want to deploy the classes before any of
> > > the dd's, and
> > > separate all the dd's from any classes.
> > >
> > > You can't have 2 versions of the same class. They will
> > > interfere, as you
> > > discovered.
> > >
> > > Basically we decided that we would initially support
> > > visibility between
> > > deployment packages with hot-redeploy, since this is a
> > > feature previously
> > > unavailable anywhere as far as I know. Once this is
> > > thoroughly stable and
> > > well tested we will consider whether it is really advisable
> > > to have several
> > > of these sets of UnifiedClassLoaders at once in one vm.
> For now, you
> > > should run several jboss servers in different vms.
> > >
> > > david jencks
> > >
> > > >
> > > > Hunter
> > > >
> > > > > From: David Jencks <[EMAIL PROTECTED]>
> > > > > Reply-To: [EMAIL PROTECTED]
> > > > > Date: Thu, 16 May 2002 18:59:18 -0400
> > > > > To: [EMAIL PROTECTED]
> > > > > Subject: Re: [JBoss-user] Does JBoss3 have Problems
> > > Deploying Similar
> > > > ejb-jars
> > > > > in Different EARs
> > > > >
> > > > > JBoss 3 doesnt' support having 2 classes with the same
> > > name, no matter
> > > > how
> > > > > you package them. It does support classes in one ear
> seeing the
> > > > classes in
> > > > > the other ear(s).
> > > > >
> > > > > david jencks
> > > > >
> > > > > On 2002.05.16 18:03:07 -0400 Hunter Hillegas wrote:
> > > > >> I'm trying to get this damn EAR to deploy and I started
> > > wondering if
> > > > >> JBoss3
> > > > >> has trouble deploying an EAR if another EAR has a
> > > similar ejb-jar...
> > > > >>
> > > > >> Basically I have two versions of an ejb-jar. One has a
> > > bean with one
> > > > >> extra
> > > > >> CMP variable.
> > > > >>
> > > > >> The first archive deploys just fine. The second one
> > > deploys okay if
> > > > the
> > > > >> first is not deployed. If the first one is deployed
> and I try to
> > > > deploy
> > > > >> the
> > > > >> second then I get a message that the bean class doesn't
> > > contain an
> > > > >> accessor
> > > > >> for the extra variable that exists in the second ejb-jar...
> > > > >>
> > > > >> Any ideas?
> > > > >>
> > > > >> Hunter
> > > > >>
> > > > >>
> > > > >>
> _______________________________________________________________
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> > > > >
> > > > >
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