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From Nicola Ken Barozzi <nicola...@apache.org>
Subject Re: JMX Integration
Date Mon, 02 Sep 2002 13:41:58 GMT

Stephen McConnell wrote:
> Peter Donald wrote:
>  >On Mon, 2 Sep 2002 02:45, Huw Roberts wrote:
>  >
>  >
>  >>>>Rather than this I think I may prefer something simpler - at least
>  >>>>initially. Something like
>  >>>>
>  >>>>BlockContext.register( String topic, String name, Object object )
>  >>>>BlockContext.unregister( String topic, String name )
>  >>>>
>  >>>>Job jobOne = ... get the job somehow
>  >>>>ctx.register( "jobs", jobOne.getName(), jobOne );
>  >>>>...
>  >>>>ctx.unregister( "jobs", jobOne.getName() );
>  >>>>
>  >>>>The reason for this is that then we don't have to expose SystemManager
>  >>>>to clients and thus we are free to evolve it as we see fit. However
>  >>>>exposes all the information needed to manage object.
>  >>>>Like?
>  >>>>
>  >>>>
>  >>I have 3 issues:
>  >>1) The ability to add more than one level of hierarchy beneath the 
> blocks.
>  >>2) Using an interface will make the client code cleaner and more 
> portable.
>  >>3) Client code will be hooking into this, meaning we are committed to
>  >>supporting it going forward.
>  >>
>  >>I can live with this for now, but i want to consider how it fits into
>  >>the longer term direction.  What I'd like to do, is add a
>  >>ManagementContext interface to Framework, and then have SystemManager
>  >>extend this.  That would be the first step towards making the
>  >>functionality available in other containers.  Does that sound ok?  If
>  >>so, how do we proceed in that direction?  If its not too big a deal
>  >>maybe we could skip this intermediate step?
>  >>
>  >>
>  >
>  >I would still prefer to go with the
>  >
>  >BlockContext.register( String topic, String name, Object object )
>  >BlockContext.unregister( String topic, String name )

-1 a Context should never be used by a Container for its services.
If it is used, it's basically giving a service to everyone without IoC.

> >The reason is that we have discussed that feature in the past without 
>  > really coming to any conclusion.
> Adding behaviour to an context implementation over and above the
> framework defintion of context means that you are defining a
> specilization of the Avalon Component Model for Phoenix.  Components
> that include a dependency on that model are no longer portable.
> Alternative solutions to introducing the functionality you are
> describing is totally possible without introducing the complication
> associated with BlockContext - i..e. use the context object to aquire an
> abject implementing the interface the component needs, then apply
> register/unregister against that interface, or, havbe the copmponent
> declare a depedency on a registery service of some kind.

I resist also this, since we are using services in a context, rather 
than be given them by the Container.

I have looked in the archives and seen that once upon a time, Context 
was indeed used as a common service, and a common place to put services.

I think that Context should never keep services where possible.

For example, ServletContext is about instance data, not services.

> This was discussed in respect to the shutdown request handler - this
> requirement is no different.

Nicola Ken Barozzi                   nicolaken@apache.org
             - verba volant, scripta manent -
    (discussions get forgotten, just code remains)

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