Gemstone/J
jim
----- Original Message -----
From: "Luis Canals" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, September 26, 2000 12:55 PM
Subject: Re: Using singleton from EJBs (not implementing singleton with EJ B!)
> Which EJB containers use multiple VM's?
>
> -----Original Message-----
> From: Dave Wolf [mailto:[EMAIL PROTECTED]]
> Sent: martes, 26 de septiembre de 2000 17:32
> To: [EMAIL PROTECTED]
> Subject: Re: Using singleton from EJBs (not implementing singleton with
> EJB!)
>
>
> >
> > >
> > > A singleton pattern will not be very portable. Even if the
> > static member
> > > were portable which it is not, the use of custom ClassLoaders by most
> > > containers will likely cause issues with your pattern.
> > >
> >
> > It seems it would not be portable only if you want a singleton for all
> > containers in cluster. But a singleton seems very portable and applicable
> > in situations where you want a singleton object per container and do not
> > need to share that singleton between multiple containers.
>
> Not necesarilly. Its of course not a singleton across containers, but it
> may not even be a singleton within the same container.
>
> 1) The container may use multiple VM's
> 2) More common, the container may use a custom ClassLoader to load the
> classes in order to support features like hot swapping. If so, the
> singleton will only be unqique across a ClassLoader. Or, a more comman
> issue would be as per the J2EE spec, each web app must have its own
> ClassLoader. Meaning the singleton is only truly a singleton within the
> single web application.
>
> Dave Wolf
> Internet Applications Division
> Sybase
>
>
>
>
> >
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