Hands-On Reactive Programming in Spring 5

Factory method – generate

The generate factory method is designed to allow for the creation of complicated sequences based on an internal forwarded state of the generator. It requires an initial value and a function, which calculates the next internal state based on the previous one and also sends the onNext signal to a downstream subscriber. For example, let's create a simple Reactive Stream that produces the Fibonacci sequence (1, 1, 2, 3, 5, 8, 13, ...). The code for this task may look as follows:

Flux.generate(                                                     // (1)    () -> Tuples.of(0L, 1L),                                       // (1.1)          (state, sink) -> {                                             //        log.info("generated value: {}", state.getT2());            //        sink.next(state.getT2());                                  // (1.2)        long newValue = state.getT1() + state.getT2();             // return Tuples.of(state.getT2(), ...