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From "Johan Lindquist" <jo...@kawoo.co.uk>
Subject Re: [HiveMind] HiveMind ideas
Date Thu, 04 Mar 2004 08:33:21 GMT

>>
>> - One of the things we need to be able to do is to choose particular
>> service implementations at startup time, based on property or
>> preference
>> settings.  In particular, I'd like to be able to swap out all remote
>> services in favor of local (dummy) services based on a single property
>> value; or choose local over remote on a service-by-service basis.  The
>> only way I can think of to do this sort of thing in a general
>> way would
>> be to have some kind of boolean expression associated with a service
>> implementation that tells HiveMind whether to use that
>> implementation or
>> to go on to the next available implementation.  (I guess I'm thinking
>> OGNL or something equivalent.)  Any thoughts on how I could accomplish
>> this within the current HiveMind implementation?
>
> I've thought about this as well. The approach I'm going to explore is
> a "broker" core service implementatation factory. It will be provided  
> with descriptions
> of other services and can dynamically select one.
>
> So, you might have module.PublicService by the service id referenced in  
> your code (or injected into
> other services).  Its builder will select either module.StandardService  
> or module.DebugService at
> runtime.

Would this be limited to the builder or could it be extended to include  
run-time dynamic service lookups too?  I have on a couple of occasions had  
to write a simple broker to select the correct implementation at runtime -  
several services implement the same interface and register with the  
selector by injecting their meta-data into its configuration.

Now, the meta-data in these cases was very simple (for example, just an id  
and a service-id) and making this generic is much a bigger job but having  
this ability within HiveMind (and therefore not having to 'cook' a new  
broker for each service interface that requires it) would be great.  I  
guess what it boils down to is that I miss the selectors in Avalon a  
little but that is the only thing i do miss :)

Johan

-- 
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