[cdi-dev] What about @AsyncObserves ?

Antoine Sabot-Durand antoine at sabot-durand.net
Thu Mar 19 10:36:50 EDT 2015

Hi guys,

So it seems impossible to avoid opt-in on the observer side for the sake of awkward compatibility.
Adding a member to @Observes could also be a source of issues when old CDI lib will be used with CDI 2.0 runtime. Some of us (including me) don’t want to add an @Async annotation to CDI spec, so perhaps we should add an async alternative to @Observes with an @AsyncObserves or @ObservesAsync ?

So it would be

public void myObserver(@AsyncObserves payload) {}

instead of

public void myObserver(@Observes payload) {}

Pros :
- it’s a cleaner way to manage the opt-in than to put 2 annotations or add a member to an existing one
- it could have new members related to async behavior (context propagation, concurrent scenario, etc…)
- As it won’t be in legacy code no risk to see old observers called asynchronously

Cons :
- Still not clear for users when fire() is called to see @AsyncObserves launched synchronously
- Yet another annotation added

wdyt ?

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