Mono

• 0개 또는 1개의 데이터를 emit하는 Publisher이다(Compare with RxJava Maybe)

• Data Emit 과정에서 에러가 발생하면 OnError Signal을 Emit 한다

  

  Mono.just("Hello, Reactor!")
              .subscribe(data -> log.info("# emitted data: {}", data));
  

  Mono.empty()
              .subscribe(
                      data -> log.info("# emitted data: {}", data),
                      error -> {},
                      () -> log.info("# emitted onComplete Signal")
              );
  

  URI worldTimeUri = UriComponentsBuilder.newInstance()
                  .scheme("https")
                  .host("worldtimeapi.org")
                  .port(443)
                  .path("api/timezone/Asia/Seoul")
                  .build()
                  .encode()
                  .toUri();
  
          RestTemplate restTemplate = new RestTemplate();
          HttpHeaders httpHeaders = new HttpHeaders();
          httpHeaders.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
  
          Mono.just(
                  restTemplate.exchange(worldTimeUri, HttpMethod.GET, new HttpEntity<>(httpHeaders), String.class)
          )
                  .map(response -> {
                      DocumentContext jsonContext = JsonPath.parse(response.getBody());
                      return jsonContext.<String>read("$.datetime");
                  })
                  .subscribe(
                          data -> log.info("# emitted data: {}", data),
                          error -> log.error(error.getMessage(), error),
                          () -> log.info("# emitted onComplete Signal")
                  );
  

Flux

• 0개 ~ N개의 데이터를 Emit 하는 Publisher 이다

• 데이터 Emit 과정에서 에러가 발생하면 onError Signal을 Emit 한다

  

  Flux.just(6, 9, 13)
                  .map(num -> num%2)
                  .subscribe(remainder -> log.info("# remainder: {}", remainder));
  

  Flux.fromArray(new Integer[] {3, 6, 7, 9})
                  .filter(num -> num > 6)
                  .map(num -> num*2)
                  .subscribe(multiply -> log.info("# multiplied: {}", multiply));
  

  Flux<Object> flux = Mono.justOrEmpty(null).concatWith(Mono.justOrEmpty("Jobs"));
          flux.subscribe(data -> log.info("# emitted data: {}", data));
  

  Flux.concat(
                  Flux.just("Venus"),
                  Flux.just("Earth"),
                  Flux.just("Mars")
          )
                  .collectList()
                  .subscribe(planetList -> log.info("# planets: {}", planetList));