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From Berin Loritsch <blorit...@apache.org>
Subject Re: Future Direction for Avalon
Date Thu, 08 May 2003 12:23:33 GMT
Leo Sutic wrote:
> 
>>From: Niclas Hedhman [mailto:niclas@hedhman.org] 
>>
>>Sharing of components between containers will introduce very 
>>interesting classloading issues, if you intend to support 
>>reloadable containers and/or components.
> 
> 
> Not much more or less than when you have reloadable components
> in one container. I believe interceptors are a standard way
> of solving these things at a purely technical level, whether
> it is in-VM or distributed.
> 
> The problem is that Avalon components in general do not have 
> defined semantics for reloading. For example, when a component
> is reloaded, it loses its internal state. EJBs solve that by
> storing themselves or by being stateless. There is no
> equivalent protocol for Avalon components.
> 
> Actually, I think the Fortress/ECM usage pattern may have an
> advantage here - since you, whenever you use the component,
> have to look it up, use it, and release (whereas the Phoenix
> usage pattern means you look up all components in compose()
> and release them (optinally) in dispose()), means that we
> can easily see when the user of a component is finished with
> it and doesn't expect it to preserve state. This means that
> for each component that is to be reloaded, we can block
> lookup()s and only allow release(). When all instances
> are released - reload.
> 
> So simple in theory...


Bear in mind that all the components are proxied in all of the
containers.  That means that we can hold the proxy and have the
proxy block until the new instance of the component is set.
That is an option we have now.


-- 
"You know the world is going crazy when the best
rapper is a white guy, the best golfer is a black guy,
The Swiss hold the America's Cup, France is
accusing the US of arrogance, and Germany doesn't want
to go to war. And the 3 most powerful men in America
are named 'Bush', 'Dick', and 'Colon' (sic)".

-----Chris Rock


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