Flow is a Kotlin Coroutines related cold asynchronous
stream of the data, that emits from zero to N (where N
can be unbounded) values and completes normally or with
an exception.
It is conceptually the Coroutines equivalent of Flux with
an extension oriented API design, easy custom operator
capabilities and some suspending methods.
This commit leverages Flow <-> Flux interoperability
to support Flow on controller handler method parameters
or return values, and also adds Flow based extensions to
WebFlux.fn. It allows to reach a point when we can consider
Spring Framework officially supports Coroutines even if some
additional work remains to be done like adding
interoperability between Reactor and Coroutines contexts.
Flow is currently an experimental API that is expected to
become final before Spring Framework 5.2 GA.
Close gh-19975
a8d6ba9965