[cdi-dev] [JBoss JIRA] (CDI-408) bean-discovery-mode="annotated" and Producers/Observers in @Dependent beans

Antoine Sabot-Durand (JIRA) issues at jboss.org
Tue Mar 11 01:45:11 EDT 2014

    [ https://issues.jboss.org/browse/CDI-408?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12951813#comment-12951813 ] 

Antoine Sabot-Durand commented on CDI-408:

Honestly I don't understand [~struberg]. Today in CDI 1.0 and in CDI 1.1 with {{bean-discovery-mode=all}} mode we do these deep class analysis. So the code is already there in implementations. Ok, it probably has to be adapted but it don't see where is the "much more work" in term of dev.
Solution at the impl level are multiple :

 * Start as if we where in {{bean-discovery-mode=all}} and use the same mechanism that reject non eligible class (after finding no default constructor for instance) or that {{@Vetoed}} it, if it doesn't contain bean defining annotation
 * Use annotation processing to decide at compile time.

My understanding of the {{annotated}} bean discovery mode is not about optimization, it's about CDI automatic activation. If it's optimized it's better but the first goal is to provide CDI implicitly. For me it's not important if the {{annotated}} bean discovery mode take the same amount of time at boot time than {{all}} bean-discovery-mode and that's the only risk we take here in term of "much more work".
IMO The real question is "does this feature is interesting for the end user ?" and then "how much does it costs in terms of dev and perf ?".
In this particular case I won't say the feature is awesome but the lack of it is very not user friendly.
We have zillion forum post and stack exchange "bug" out there about CDI 1.0 users forgetting {{beans.xml}} in their app. Now that we provide the mean in CDI 1.1+ to get rid of this file I really think we should do it as complete as possible.

Regarding the producer method in superclass, I'm not sure to totally understand your use case. Can you give an example ?
> bean-discovery-mode="annotated" and Producers/Observers in @Dependent beans
> ---------------------------------------------------------------------------
>                 Key: CDI-408
>                 URL: https://issues.jboss.org/browse/CDI-408
>             Project: CDI Specification Issues
>          Issue Type: Clarification
>          Components: Beans
>            Reporter: Jens Schumann
>            Assignee: Antoine Sabot-Durand
>              Labels: CDI_spec_chge
>             Fix For: 1.2 Proposed
> Right now bean-discovery-mode="annotated" skips beans that are not annotated with an bean-defining annotation even if they contain an observer method or producer method/field. I would not recommend having (not annotated) @Dependent beans with @Observes or @Produces - I just had them by accident while playing around with Wildfly.
> However there are two impacts:
> 1. Someone might be confused by ignored @Producer's. Not a major issue here, the CDI runtime will report it. We could optionally document the behavior in the spec, so it's clear to everyone. However I think it's inconsistent, since @Produces may contain a scope (and has a default scope too). Therefore I would vote for @Produces support in bean-discovery-mode="annotated". Of course the enclosing class is not a managed bean that may be injected somewhere.
> 2. Since Observer methods in "not annotated" beans fail silently this can be a major issue for applications, especially if you migrate from CDI 1.0 (CDI 1.0 source code and CDI 1.0 thinking model). Therefore I believe @Observer methods have to be included in bean-discovery-mode="annotated" even if the enclosing bean does not have a bean-defining annotation. Of course the enclosing class is not a managed bean that may be injected somewhere.
> I understand that the proposal above might have negative impacts on class scanning performance in bean-discovery-mode="annotated". However silently failing @Observes can be a major cause of defects that have to be treated because of technical and political reasons. Technical - because it may cause bugs. And political - because in my experience many people are still skeptical that CDI events are a trustworthy achievement[1]. Possibly skipped observer methods won't make live easier.
> If you believe the proposal would kill the original intent of bean-discovery-mode="annotated" please document the impact for Producers and Observers in the spec and even in the XSD.
> --
> [1] I have trained a couple hundred people in using CDI and CDI events. And every time I have to argument against the uncertainty on event delivery: "How do I know which observers are active?", "Who ensures that event's are delivered?"... I personally LOVE events;)
> Btw: Which JIRA version is CDI 1.1 Final? 

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