12 Replies Latest reply on Dec 15, 2009 6:51 PM by pmuir

What about qualifying a conversation?

agori Nov 19, 2009 12:52 PM

I need to begin a conversation. I'd like that DI inside the conversation narrows bean selection using the qualifiers that I pass as parameter. For example:

conversation.begin();
conversation.qualify(new AnnotationLiteral<A>(){});

Then if

@Inject Bean bean;

and

@A class ABean extends Bean {
}

ABean is injected instead of Bean. Is this feature already available or not and is a stupid request?

1. Re: What about qualifying a conversation?

nickarls Nov 19, 2009 12:54 PM (in response to agori)

I don't quite follow. Are you talking about Specialization? Or are you referring to filtering the stuff in the conversation scope somehow?
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2. Re: What about qualifying a conversation?

agori Nov 19, 2009 2:37 PM (in response to agori)
Yes specialization.
One conversation should inject ABean, another conversation could inject BBean, another one CBean, depending on some parameter I pass to the conversation.

If a Facelets page is under the first conversation and I code:

#{bean}

Expression Language should return an instanceof of type ABean. Do you understand?

This is the API I have in mind, but it could be achievable in some other way that I don't know...
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3. Re: What about qualifying a conversation?

gavin.king Nov 19, 2009 8:53 PM (in response to agori)

It sounds a bit like the activities stuff we had in older drafts of the CDI spec (which was removed). It sounds like you want a set of bean definitions that are local to a certain business task or process. Weld does not support this, however, you can localize bean definitions to a certain module. I would say that is your best bet, if I'm understanding your requirements correctly. Put each task or process in its own jar.
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4. Re: What about qualifying a conversation?

nickarls Nov 19, 2009 9:06 PM (in response to agori)

Is the activity-stuff going away from Weld, too, or is there some use for it?
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5. Re: What about qualifying a conversation?

gavin.king Nov 19, 2009 9:58 PM (in response to agori)

Does Weld actually implement that stuff?? I didn't know...

Yes, it's useful. It could easily find it's way back into CDI 1.1.
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6. Re: What about qualifying a conversation?

nickarls Nov 20, 2009 8:05 AM (in response to agori)

I don't know if it's functional/used, just noticed some references to it in BeanManager. And since most other obsolete stuff has been cleaned out, I assumed it's there for a reason...
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7. Re: What about qualifying a conversation?

agori Nov 20, 2009 9:23 AM (in response to agori)
I don't know what is an activity in CDI. Anyway modularization in different jar or packages doesn't fit well in my situation.
I could explain with a use case. We have a web application for insurances. User login, then:

select an insurance product, named prod1.

WELD start a conversation, the main bean is ProductBean

ProductBean cooperate with interface Service. Every Service implementation should has the same name, because product.xhtml references the bean: #{myService}

Ok, here developer coded two Service implementation: Prod1ServiceBean, and Prod2ServiceBean.
If user selected prod1 then WELD should inject Prod1ServiceBean into ProductBean. If prod2 was selected WELD should inject Prod2ServiceBean...

It's like deciding injection rules at runtime.
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8. Re: What about qualifying a conversation?

nickarls Nov 20, 2009 9:59 AM (in response to agori)
Sounds like a job for @Produces?

@Inject @Any Instance<ProdService> allProdServices; @Produces @ConversationScoped ProdService getProdService() { if (reallyComplexlogic) { return allProdServices.selectStuff; } else { return allProdServices.selectOtherStuff; } }

scoping may wary depending on where the choise is made. For mid-conversation changes, you might even want to work directly with the InstanceBean...
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9. Re: What about qualifying a conversation?

agori Nov 20, 2009 10:12 AM (in response to agori)

Yes thanks, after explosing clearly the problem I realized too that it could be job for @Produces ;).
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10. Re: What about qualifying a conversation?

nickarls Nov 20, 2009 1:39 PM (in response to agori)

Speaking of obsolete stuff, is the concept of policy also something of the past? There are plenty of refs around in the code but I didn't find anything in the specs
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11. Re: What about qualifying a conversation?

nickarls Nov 20, 2009 2:15 PM (in response to agori)

Nevermind, seems to be alternatives
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12. Re: What about qualifying a conversation?

pmuir Dec 15, 2009 6:51 PM (in response to agori)

Nicklas Karlsson wrote on Nov 20, 2009 08:05:

I don't know if it's functional/used, just noticed some references to it in BeanManager. And since most other obsolete stuff has been cleaned out, I assumed it's there for a reason...

Yup, Gavin told me to keep it in as IBM wanted it :-)
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