Gemstone.
-----Original Message-----
From: Luis Canals [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, September 26, 2000 10:26 PM
To: [EMAIL PROTECTED]
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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