[cdi-dev] Adding Lambdas as CDI beans

[John D. Ament]

Sven,

I'm a little curious, why do they need to avoid serializable contexts?  In
all honesty, I use app scoped functions, predicates in my code, at least in
a couple of places.  Lambdas are specifically meant for operations, not
data, so they should be in a highly reusable scope (in my opinion at least).

On the flip side, I have a hard time justifying needing to provide
injectable beans for lambdas since good encapsulation should indicate
they're only used in a single spot.

John

On Sat, Oct 17, 2015 at 7:51 AM Sven Linstaedt <sven.linstaedt at gmail.com>
wrote:

> Just one question: Who is on charge and is able of managing this unmanaged
> instances, e.g. lifecycle, serialization, concurrency (e.g. when dealing
> with closures)?
>
> Functional programming and DI seem to be somehow disjunct in this case.
> E.g. manually setting up observers seem to better fit extension than normal
> application code.
>
> On the other side, specifying producer methods or fields, that are
> injectable and return lambda expressions seems to be a no brainier for CDI,
> is not it? As long as they are not scoped in a serializable context.
>
> Have a nice weekend
> Sven
>
> -- sent by phone
>
> Am 17.10.2015 um 11:06 schrieb David Blevins <david.blevins at gmail.com>:
>
> In brainstorming mode about fun that could be made possible with Java 8
> and Java EE.
>
> Question in my mind is: is there some way we could make it possible for
> Lambdas or Method Refs to be CDI beans?
>
> It goes against the grain obviously as CDI creation is very much a “Don’t
> call us, we’ll call you” kind of thing.  The VM dynamically creates a
> wrapper object around the Lambda or method reference and it implements the
> given interface.
>
> To make it work, there would need to be some non-producer method way of
> saying “put this thing in the context with these qualifiers”.
>
> Imagine a method somewhere that would allow you to:
>
>    public <T> void addObserver(java.util.function.Consumer<T> observer,
> Annotation... qualifiers);
>
>
> Then you could take advantage as follows:
>
>    final List<URI> uris = new ArrayList<>();
>    // @Observes URI
>    addObserver((Consumer<URI>) uris::add);
>
>    // @Observes Thread
>    addObserver(Runtime.getRuntime()::addShutdownHook);
>
>    // @Observes Runnable
>    addObserver((Consumer<Runnable>)
> Executors.newFixedThreadPool(3)::submit);
>
>    // @Observes URI
>    addObserver((Consumer<URI>) System.out::println, new
> AnnotationLiteral<Fine>() {
>    });
>
>    // @Observes Handler
>    final Logger logger = Logger.getLogger("somewhere");
>    addObserver(logger::addHandler); // add handlers via event
>
>    // @Observes @Fine String
>    addObserver((Consumer<String>) logger::fine, new
> AnnotationLiteral<Fine>() {});
>    }
>
>
>
> -David
>
>
>
> --
> David Blevins
> http://twitter.com/dblevins
> http://www.tomitribe.com
>
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