Convert from Flux to Mono

Question

How can I convert from a Flux with 1 element to a Mono?

Flux.fromArray(arrayOf(1,2,1,1,1,2))
                .distinct()
                .take(1)

How do I make this a Mono(1)?

Answer 1

Instead of take(1), you could use next().

This will transform the Flux into a valued Mono by taking the first emitted item, or an empty Mono if the Flux is empty itself.

Answer 2

Here is a list:

• Flux#single will work if there is one element from Flux. Eg: flux.take(1).single();

• Flux#next will get you the first element. Eg: flux.next();

• Flux#last for last element. Eg: flux.last();

• Flux#singleOrEmpty is similar to Optional. Eg: flux.take(0).singleOrEmpty();

• Flux#collect, it depends on use case.

    flux.collect(Collectors.reducing((i1, i2) -> i1))
        .map(op -> op.get());
  

• Flux#elementAt for i'th index. Eg: flux.elementAt(1);

• Flux#shareNext for first found element. flux.shareNext();

• Flux#reduce for reduction op. Eg: flux.reduce((i1,i2) -> i1);

Answer 3

Or,you could use single() on the filtered Flux

Answer 4

Also the very simple way is to use Mono.from()

Mono<Integer> mono = Mono.from(flux);

If your flux has more than one element, then it will just take the first element emitted by the flux.