Hands-On Reactive Programming in Spring 5

Materializing and dematerializing signals

Sometimes, it is useful to process a stream not in terms of data, but in terms of signals. To convert a stream of data into a stream of signals and back again, Flux and Mono provide the materialize and dematerialize methods. An example of this is as follows:

Flux.range(1, 3)
    .doOnNext(e -> log.info("data  : {}", e))
    .materialize()
    .doOnNext(e -> log.info("signal: {}", e))
    .dematerialize()
    .collectList()
    .subscribe(r-> log.info("result: {}", r));

The preceding code produces the following output:

data  : 1
signal: onNext(1)
data  : 2
signal: onNext(2)
data  : 3
signal: onNext(3)
signal: onComplete()
result: [1, 2, 3]

Here, when processing the signal stream, the doOnNext method receives not only onNext ...