Consuming Arrays from CompletableFutures with Uni / Multi

[mikeymop]

Hello,

I have gone through the examples a few times and am still a little shaky on the concepts.
I am trying to consume a list of buckets from Amazon S3 using Quarkus's Async version of the library.

With this library, listBuckets() returns a ListBucketsResponse which is an abstract of CompletableFuture.
If I call .get().buckets() on the response I get a List<Buckets>.

What I think I want is to return a Uni<List<Bucket>> such that when I consume my method I can just call .await() and get back a List.

Using Multi I am able to get back a List<Buckets> using Multi.createFrom().items(s3.listBuckets().get().buckets()); however this is difficult to consume.
I got the inspiration to try with Multi from this examle this example.
However I am missing something from this example where a CompletableFuture is converted in a completionStage().

After reading the concepts again, I believe I do in fact want a Uni as this will either return a list of Buckets or it will return an error.

Can someone help expand on the concepts for me in the context to consuming a Future of a List?

[cescoffier]

If I understood correctly, you have something like:

CompletableFuture<List<Bucket>> retrieveBucketsUsingS3AsyncApi();

To obtain a Uni<List<Bucket>>, just use:

Uni<List<Bucket>> uni = Uni.createFrom().completionStage(() -> retrieveBucketsUsingS3AsyncApi());

If you need a Multi<Bucket>, use:

Multi<Bucket>> uni = Multi.createFrom().uni(() -> Uni.createFrom().completionStage(() -> retrieveBucketsUsingS3AsyncApi()))
   .map(list -> Multi.createFrom().items(list));