經驗分享：將微服務遷移到Spring WebFlux - allegro.tech

Pizza getPizzaBlocking(int id) {
    try {
        return restTemplate.getForObject("http://localhost:8080/pizza/" + id, Pizza.class);
    } catch (RestClientException ex) {
        throw new PizzaException(ex);
    }
}

Mono<Pizza> getPizzaReactive(int id) {
    return webClient
        .get()
        .uri("http://localhost:8080/pizza/" + id)
        .retrieve()
        .bodyToMono(Pizza.class)
        .onErrorMap(PizzaException::new);
}

Pizza getPizzaBlocking(int id) {
    return getPizzaReactive(id).block();
}

//parallel call to two services using Java8 CompletableFuture
Food orderFoodBlocking(int id) {
    try {
        return CompletableFuture.completedFuture(new FoodBuilder())
            .thenCombine(CompletableFuture.supplyAsync(() -> pizzaService.getPizzaBlocking(id), executorService), FoodBuilder::withPizza)
            .thenCombine(CompletableFuture.supplyAsync(() -> hamburgerService.getHamburgerBlocking(id), executorService), FoodBuilder::withHamburger)
            .get()
            .build();
    } catch (ExecutionException | InterruptedException ex) {
        throw new FoodException(ex);
    }
}

//parallel call to two services using Reactor
Mono<Food> orderFoodReactive(int id) {
    return Mono.just(new FoodBuilder())
        .zipWith(pizzaService.getPizzaReactive(id), FoodBuilder::withPizza)
        .zipWith(hamburgerService.getHamburgerReactive(id), FoodBuilder::withHamburger)
        .map(FoodBuilder::build)
        .onErrorMap(FoodException::new);
}

Mono<Pizza> getPizzaReactive(int id) {
    return Mono.fromSupplier(() -> getPizzaBlocking(id))
        .subscribeOn(Schedulers.fromExecutorService(executorService));
}

Food orderFood(int id) {
    FoodBuilder builder = new FoodBuilder().withPizza(new Pizza("margherita"));

    hamburgerService.getHamburgerReactive(id).doOnNext(builder::withHamburger);
    //hamburger will never be set, because Mono returned from getHamburgerReactive() is not subscribed to

    return builder.build();
}

Food getFoodBlocking(int id) {
    return foodService.orderFoodReactive(id).block();
}

block()/blockFirst()/blockLast() are blocking, which is not supported in thread reactor-http-nio-2

Mono<Food> getFood(int id) {
    return foodService.orderFood(id)
        .delayElement(Duration.ofMillis(1000));
}

Mono<Food> getFood(int id) throws InterruptedException {
    return foodService
      .orderFood(id)
      .doOnNext(food -> Thread.sleep(1000));
}

Mono<Pizza> getPizzaReactive(int id) {
    return webClient
        .get()
        .uri("http://localhost:8080/pizza/" + id)
        .retrieve()
        .onStatus(HttpStatus::is5xxServerError, clientResponse -> Mono.error(new Pizza5xxException()))
        .bodyToMono(Pizza.class)
        .onErrorMap(PizzaException::new);
}

ERROR 3042 --- [ctor-http-nio-5] io.netty.util.ResourceLeakDetector       : LEAK: ByteBuf.release() was not called before it's garbage-collected. See http://netty.io/wiki/reference-counted-objects.html for more information.

String valueFromCache = "some non-empty value";
return Mono.justOrEmpty(valueFromCache)
    .switchIfEmpty(Mono.just(getValueFromService()));
   

String valueFromCache = "some non-empty value";
return Mono.justOrEmpty(valueFromCache)
    .switchIfEmpty(Mono.fromSupplier(() -> getValueFromService()));