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From Stephen McConnell <mcconn...@osm.net>
Subject Re: Using Service / Component Selector in Phoenix
Date Tue, 11 Jun 2002 13:03:11 GMT


The document 
http://jakarta.apache.org/avalon/phoenix/guide-example-configuration.html 
contains a description of how to handle this inside Phoinix.

Cheers, Steve.


Andrei Ivanov wrote:

>Hi,
>I came across with simple problem (I think it is simple for experienced
>Avalon developers) with my Phoenix-based application.
>
>The problem is as follows:
>I have phoenix service which contract is defined in interface
>
>A. ServiceInterface
>
>I have two different block which offer service A (in other words different
>implementation for the same service):
>
>Blocks
>B. offers A
>C. offers A
>
>B and C should be configured and initialized differently as well as they
>will depend on different services.
>
>I would like to be able to specify which block will be used (B or C) to
>provide service A changing only configuration (config.xml) file.
>Can anyone give me example how to achieve that and what is the standard
>practice for Phoenix-based application for this?
>
>Regards,
>Andrei
>
>
>
>----- Original Message -----
>From: "Peter Royal" <proyal@apache.org>
>To: "Avalon-Phoenix Developers List" <avalon-phoenix-dev@jakarta.apache.org>
>Sent: Monday, June 10, 2002 5:44 PM
>Subject: Re: Constraints on dependencies
>
>
>  
>
>>On Thursday 06 June 2002 07:43 pm, Peter Donald wrote:
>>    
>>
>>>1. Are constraints container specific or not?
>>>2. Is there a subset of constraints that are container agnostic?
>>>3. How do we represent constraints in the system? An opaque string? A
>>>Configuration tree? An XPath expression?
>>>4. Do the providers or the Kernel validate the constraints?
>>>5. Do the providers get informed that they must conform to certain
>>>constraints?
>>>6. Does validation occur at initialization time or assembly time?
>>>
>>>My answers would be;
>>>      
>>>
>>1. Sometimes. I haven't seen any container-specific examples yet though ;)
>>2. Yes. Mainly anything that involves lookup( ROLE ), ie. component
>>    
>>
>assembly
>  
>
>>3. XPath or other evaluated expression :)
>>4. Kernel
>>5. No, but there may be cases where they need to be queried by the kernel
>>    
>>
>for
>  
>
>>constraint resolution (like the ORB example. the kernel will most likely
>>    
>>
>be
>  
>
>>unaware that its ORB component hosts others)
>>6. Both. As much as possible should be done at assembly, but I'm sure some
>>must be defered to init time.
>>
>>    
>>
>>>The problem is basically that in some cases it is going to be
>>>      
>>>
>practically
>  
>
>>>impossible for kernel to validate the constraint unless the provider
>>>conforms to very specific contracts or is self validating.
>>>      
>>>
>>I agree. I'd opt more for the "specific contracts" option, which could be
>>    
>>
>as
>  
>
>>easy as exposing MetaInfo classes.
>>-pete
>>
>>--
>>peter royal -> proyal@apache.org
>>
>>--
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>>    
>>
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>  
>
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>>    
>>
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>  
>
>
>
>--
>To unsubscribe, e-mail:   <mailto:avalon-phoenix-dev-unsubscribe@jakarta.apache.org>
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>
>  
>

-- 

Stephen J. McConnell

OSM SARL
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mailto:mcconnell@osm.net
http://www.osm.net




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