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From Christian Essl <christiane...@yahoo.de>
Subject Re: [Hivemind] ServiceImplementationFactory - no Exception (?)
Date Wed, 17 Mar 2004 13:26:12 GMT
> But, if I'm a client and I call registry.getService() I absolutely want a
> service or an exception! Otherwise I have to stick null checks in all 
> over

I agree. Actullay I was always expecting HiveMind to do that. This is also 
more consistent, because if the module or the ServiceExtensionPoint is not 
found an ApplicationRuntimeException is thrown.

But now I am a bit confused about where this null comes from. As I see all 
ServiceModels - except of primitive - always return a proxy, independent 
of what the factory actually returns. And the primitive ServiceModel (and 
as I think the other Models as well) uses 
AbstractServiceModelImpl.constructCoreServiceImplementation() which does 
check for null and throws an ApplicationRuntimeException.

Maybe Benjamin you could tell how you got this null. So that it could be 
reproduced on the current HiveMind from the cvs. To me it looks like a 
bug. Or maybe you used an ServiceImplementationFactory directly - Spring 
like?  Or I just miss something.

Thanks,
Christian


On Wed, 17 Mar 2004 01:34:28 -0500, Geoff Longman 
<glongman@intelligentworks.com> wrote:

> Wait a sec. Sure log errors when the modules are parsed. That makes 
> sense.
>
> But, if I'm a client and I call registry.getService() I absolutely want a
> service or an exception! Otherwise I have to stick null checks in all 
> over
> the place.
>
> Geoff
> ----- Original Message -----
> From: "Harish Krishnaswamy" <hkrishnaswamy@comcast.net>
> To: "Jakarta Commons Developers List" <commons-dev@jakarta.apache.org>
> Sent: Tuesday, March 16, 2004 10:34 PM
> Subject: Re: [Hivemind] ServiceImplementationFactory - no Exception (?)
>
>
>> Not throwing an exception is a conscious decision. HiveMind is a
>> microkernal to be thought of as a servlet container - it loads all
>> modules at startup and any problems with the descriptors will be
>> identified and logged at load time but will continue to run. I can see
>> an exception being thrown at load time when there is a problem but
>> certainly disagree with the idea of throwing exceptions at runtime. If a
>> service is not loaded properly you have two options - don't care or fix
>> it and reload it!
>>
>> -Harish
>>
>>
>> Benjamin Tomasini wrote:
>>
>> >I have started to use Hivemind and have been successful in porting over
>> >some existing work.  It is quite nice!  Very well thought out. Keeping
>> >the service / proxy layer in place is cool.
>> >
>> >One suggestion so far...
>> >
>> >I had a case where my service object from Registry.getService came back
>> >null.  One of the services used the BuilderFactory.  I was getting a
>> >log4j ERROR message, but no exception was thrown to my app.  It was a
>> >simple runtime error - a typo in a config file.
>> >
>> >Looking further, I see that
>> >
>> >in
>> >
>> >org.apache.hivemind.ServiceImplementationFactory
>> >
>> >the method
>> >
>> >createCoreServiceImplementation(....)
>> >
>> >does not throw an exception or anything.
>> >
>> >It seems that this prevents calling applications from knowing about
>> >problems creating a service.  I could always check for null in the
>> >service object, but this isn't quite right, IMO.  Especially with the
>> >lazy loading, I think burying any exception here is bad, especially for
>> >apps that depend on a large number of services.
>> >
>> >I would be willing to put some work into this and submit a patch if we
>> >think we need some exception handling here.
>> >
>> >Ben
>> >
>> >
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>> >
>> >
>> >
>> >
>>
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>
>
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-- 
Christian Essl 

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