Spring Webflux Publisher Example

This post explains how to produce or generate flux of events programmatically.

In this example, we are publishing multiplication table of given number starting from 0 to 10 and subscriber is printing each event in console.

PublisherExample.java

package com.kswaughs.webflux;

import reactor.core.publisher.Flux;

public class PublisherExample {

    public Flux<String> produceTableOf(int num) {

        return Flux.generate(
            () -> 0, // Supplier of Initial State
            (state, sink) -> {

                if (state > 10) {
                    sink.complete();
                    return state;
                }

                String calc = num + " x " + state + " = " + num * state;
                sink.next(calc);
                return state + 1;
            }, 
            state -> {
                System.out.println("Final state:" + state);
            });
    }

    public static void main(String[] args) {

        PublisherExample example = new PublisherExample();

        System.out.println("*** Table of 5 ****");
        example.produceTableOf(5).subscribe(System.out::println);

        System.out.println("\n*** Table of 3 ****");
        example.produceTableOf(3).subscribe(System.out::println);
    }
}

Output

*** Table of 5 ****
5 x 0 = 0
5 x 1 = 5
5 x 2 = 10
5 x 3 = 15
5 x 4 = 20
5 x 5 = 25
5 x 6 = 30
5 x 7 = 35
5 x 8 = 40
5 x 9 = 45
5 x 10 = 50
Final state:11

*** Table of 3 ****
3 x 0 = 0
3 x 1 = 3
3 x 2 = 6
3 x 3 = 9
3 x 4 = 12
3 x 5 = 15
3 x 6 = 18
3 x 7 = 21
3 x 8 = 24
3 x 9 = 27
3 x 10 = 30
Final state:11