mdedetrich commented on code in PR #931:
URL: https://github.com/apache/incubator-pekko/pull/931#discussion_r1452145485
##########
stream/src/main/scala/org/apache/pekko/stream/javadsl/Flow.scala:
##########
@@ -770,6 +770,47 @@ final class Flow[In, Out, Mat](delegate: scaladsl.Flow[In,
Out, Mat]) extends Gr
(s: S, out: Out) => f.apply(s, out).toScala,
(s: S) => onComplete.apply(s).toScala))
+ /**
+ * Transform each stream element with the help of a resource.
+ *
+ * The resource creation function is invoked once when the stream is
materialized and the returned resource is passed to
+ * the mapping function for mapping the first element. The mapping function
returns a mapped element to emit
+ * downstream. The returned `T` MUST NOT be `null` as it is illegal as
stream element - according to the Reactive Streams specification.
+ *
+ * The `close` function is called only once when the upstream or downstream
finishes or fails. You can do some clean-up here,
+ * and if the returned value is not empty, it will be emitted to the
downstream if available, otherwise the value will be dropped.
+ *
+ * Early completion can be done with combination of the [[takeWhile]]
operator.
+ *
+ * Adheres to the [[ActorAttributes.SupervisionStrategy]] attribute.
+ *
+ * You can configure the default dispatcher for this Source by changing the
`akka.stream.materializer.blocking-io-dispatcher` or
+ * set it for a given Source by using [[ActorAttributes]].
+ *
+ * '''Emits when''' the mapping function returns an element and downstream
is ready to consume it
+ *
+ * '''Backpressures when''' downstream backpressures
+ *
+ * '''Completes when''' upstream completes
+ *
+ * '''Cancels when''' downstream cancels
+ *
+ * @tparam R the type of the resource
+ * @tparam T the type of the output elements
+ * @param create function that creates the resource
+ * @param f function that transforms the upstream element and the resource
to output element
+ * @param close function that closes the resource, optionally outputting a
last element
+ * @since 1.1.0
+ */
+ def mapWithResource[R, T](
+ create: java.util.function.Supplier[R],
Review Comment:
Shouldn't we be using one of the interfaces in
https://github.com/apache/incubator-pekko/blob/b0fdac259bd57fdd481483f3fe9a7aec6e1ff38a/actor/src/main/scala/org/apache/pekko/japi/function/Function.scala
which are deliberately designed to be used within Pekko because they support
throwing exceptions in the `apply`?
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