[cdi-dev] Extensions and spec-related observer method injection points question

Laird Nelson ljnelson at gmail.com
Fri Feb 17 12:37:26 EST 2017

On Fri, Feb 17, 2017 at 9:30 AM Antoine Sabot-Durand <
antoine at sabot-durand.net> wrote:

> Regarding Extension being beans, it's the case, but rather special beans
> since you can't perform field, constructor or initializer injection in them.

Sure; obviously there are issues with exactly when a portable extension
"becomes" a bean.  You don't want to use "bean-like" features while the
container is still coming up.

> For observer that might be called during bootstrap (observing Object for
> instance) they will throw exception if they inject parameters as well since
> their matching beans are not resolvable yet.

Right; this was an excellent point you made earlier—specifically the part
about observing Object; the related point that other observer method
parameters might not be resolved seemed irrelevant to me, since by
definition a non-container-lifecycle-event-observing observer method would
not be invoked until deployment validation was complete—and which I had not
thought about.

> A good practice could be: use observers with personal payload without
> parameter injection and only for specific operation during bootstrap
> (Romain wrote an interesting post on the topic:
> https://blog-rmannibucau.rhcloud.com/#/post/share-data-in-cdi-extensions)
> Create a specific bean to declare your observers and inject the extension
> and other beans as parameter.

Yes; I am heading this way.  I had some shared state across lifecycle event
observers and "regular" observers and was hoping to keep that isolated to a
private instance variable but I can refactor this.

> If you really want to have your observers in your extension, inject
> BeanManager and perform the resolution with it...

That's what I'm doing now but it doesn't "read" as nicely; that's fine.

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