Reactive to Blocking
Sometimes you can only migrate part of your code to be reactive, and you need to reuse reactive sequences in more imperative code.
Thus if you need to block until the value from a Mono is available, use Mono#block()
method. It will throw an Exception if the onError event is triggered.
Note that you should avoid this by favoring having reactive code end-to-end, as much as possible. You MUST avoid this at all cost in the middle of other reactive code, as this has the potential to lock your whole reactive pipeline.
Value from Mono
Similarly, you can block for the first or last value in a Flux with blockFirst()/blockLast().
You can also transform a Flux to an Iterable with toIterable. Same restrictions as
above still apply.
Flux to iterable
