Programmatic lookup improvements

Both the reference implementation (Weld) and ArC have an enhanced version of javax.enterprise.inject.Instance that provide features that might be worth adding to the spec.

Enhancement	Description
Instance#getHandler() (name TBC)	Allows the client to obtain a “contextual reference handler” which not only holds the contextual reference but also makes it possible to inspect the metadata (i.e. Bean<?>) of the relevant bean and to destroy the underlying contextual instance.
Instance#handlers() (name TBC)	Returns an Iterable of handlers described above.
select() method that accepts java.lang.reflect.Type	This allows for generic selection of instances which can be handy while dealing with third party beans through extensions. However, it’s not type-safe.
Caching the result of Instance#get()	See https://quarkus.io/guides/cdi-reference#caching-the-result-of-programmatic-lookup

See also Weld docs about WeldInstance - Enhanced version of jakarta.enterprise.inject.Instance.

[manovotn]

FTR this issue was discussed during CDI meeting yesterday. General consensus was that the Handler feature should be added into specification (e.g. Instance#handlers() and Instance.getHandler()) while the remaining two features got mixed reactions and the decision was to be keep track of them but don’t add them to the specification just yet.

[Ladicek]

The main point of Handle is really the ability to browse beans of certain type before creating their instances. The fact that you can perform get and destroy from there is just a convenience.

I wouldn’t call it “just a convenience”, because if you getHandles() and filter based on Bean metadata and then want to create an instance, going back to the Instance would require you to 1. remember position, 2. iterate again and rely on iteration order, which is clunky and generally a bad idea. So I’d consider instantiating and destroying essential.

In any case, I just wanted to clarify for myself, and thought perhaps that would be useful for someone else too 😃