More flexible approach to activate Beans by conditions

[hantsy]

Currently, there is a @Alternative annotation, but it also needs to be declared in XML configuration to activate a Bean at runtime.

Is it possible to design a @Conditional annotation and Condition interface like Spring to activate a CDI bean in source codes without XML declarations?

@ConditionalOnProperties
@ConditionalOnBean/ConditionalOnMissingBean
@ConditionalOnClass/CondtionalOnMissingClass
@ConditionalOnModule/CondtioinalOnMissingModule(java module)
...

https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/context/annotation/Conditional.html

https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/context/annotation/Condition.html

[Ladicek]

Currently, there is a @Alternative annotation, but it also needs to be declared in XML configuration to activate a Bean at runtime.

No it doesn't. If you enable an alternative in beans.xml, it is a per bean archive enablement. You can also assign it a @Priority, which makes it per application enablement. I'd say the second variant is preferred (and the only option in CDI Lite).

Is it possible to design a @Conditional annotation and Condition interface like Spring to activate a CDI bean in source codes without XML declarations?

Possibly, but due to build-time requirements for CDI Lite, it cannot be as powerful as runtime-oriented conditions in Spring.

[hantsy]

Possibly, but due to build-time requirements for CDI Lite, it cannot be as powerful as runtime-oriented conditions in Spring.

I am not how Weld process the build time support at build time, but Micronaut also includes such similar feature https://docs.micronaut.io/latest/api/io/micronaut/context/condition/Condition.html. And there is a project under EE4J - Open DI which was trying to use Micronaut tools to impl the CDI lite. (But now it seems this project is discontinued)

[Ladicek]

We just talked about this on the CDI call and figured that at least in CDI Full, this should be possible to implement using Portable Extensions (by vetoing beans that don't satisfy the condition). If that extension becomes successful, we'd look at incorporating that into the spec.