>
> >
> > 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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