Spring webclient是非阻塞客户端吗？

Question

@GetMapping(ITEM_END_POINT_V1)
public Flux<Item> getAllItems(){
        return Flux.just(new Item(null, "Samsung TV", 399.99),
                new Item(null, "LG TV", 329.99),
                new Item(null, "Apple Watch", 349.99),
                new Item("ABC", "Beats HeadPhones", 
      149.99)).delayElements(Duration.ofSeconds(1)).log("Item : ");
}

WebClient webClient = WebClient.create("http://localhost:8080");

@GetMapping("/client/retrieve")
public Flux<Item> getAllItemsUsingRetrieve() {
        return webClient.get().uri("/v1/items")
                .retrieve()
                .bodyToFlux(Item.class).log();
}

2019-05-01 22:44:20.121  INFO 19644 --- [ctor-http-nio-2] Item :                                   : onSubscribe(FluxConcatMap.ConcatMapImmediate)
2019-05-01 22:44:20.122  INFO 19644 --- [ctor-http-nio-2] Item :                                   : request(unbounded)
2019-05-01 22:44:21.126  INFO 19644 --- [     parallel-1] Item :                                   : onNext(Item(id=null, description=Samsung TV, price=399.99))
2019-05-01 22:44:22.129  INFO 19644 --- [     parallel-2] Item :                                   : onNext(Item(id=null, description=LG TV, price=329.99))
2019-05-01 22:44:23.130  INFO 19644 --- [     parallel-3] Item :                                   : onNext(Item(id=null, description=Apple Watch, price=349.99))
2019-05-01 22:44:24.131  INFO 19644 --- [     parallel-4] Item :                                   : onNext(Item(id=ABC, description=Beats HeadPhones, price=149.99))
2019-05-01 22:44:24.132  INFO 19644 --- [     parallel-4] Item :                                   : onComplete()

2019-05-01 22:44:19.934  INFO 24164 --- [ctor-http-nio-2] reactor.Flux.MonoFlatMapMany.1           : onSubscribe(MonoFlatMapMany.FlatMapManyMain)
2019-05-01 22:44:19.936  INFO 24164 --- [ctor-http-nio-2] reactor.Flux.MonoFlatMapMany.1           : request(unbounded)
2019-05-01 22:44:19.940 TRACE 24164 --- [ctor-http-nio-2] o.s.w.r.f.client.ExchangeFunctions       : [7e73de5c] HTTP GET http://localhost:8080/v1/items, headers={}
2019-05-01 22:44:24.159 TRACE 24164 --- [ctor-http-nio-6] o.s.w.r.f.client.ExchangeFunctions       : [7e73de5c] Response 200 OK, headers={masked}
2019-05-01 22:44:24.204  INFO 24164 --- [ctor-http-nio-6] reactor.Flux.MonoFlatMapMany.1           : onNext(Item(id=null, description=Samsung TV, price=399.99))
2019-05-01 22:44:24.204  INFO 24164 --- [ctor-http-nio-6] reactor.Flux.MonoFlatMapMany.1           : onNext(Item(id=null, description=LG TV, price=329.99))
2019-05-01 22:44:24.204  INFO 24164 --- [ctor-http-nio-6] reactor.Flux.MonoFlatMapMany.1           : onNext(Item(id=null, description=Apple Watch, price=349.99))
2019-05-01 22:44:24.204  INFO 24164 --- [ctor-http-nio-6] reactor.Flux.MonoFlatMapMany.1           : onNext(Item(id=ABC, description=Beats HeadPhones, price=149.99))
2019-05-01 22:44:24.205  INFO 24164 --- [ctor-http-nio-6] reactor.Flux.MonoFlatMapMany.1           : onComplete()

我希望客户不会等待4秒然后得到实际的结果。如您所见，服务器在22:44:21.126上开始发出onNext()，客户端在22:44:24.159上获得结果。所以我不明白如果webclient有这种行为，为什么它被称为非阻塞客户端。

Answer 1

WebClient是非阻塞的，也就是说通过WebClient发送HTTP请求的线程没有被IO操作阻塞。当响应可用时，netty将通知其中一个工作线程，并且它将根据您定义的反应流操作来处理响应。

在您的示例中，服务器将等待一个Flux中的所有元素可用（4秒），将它们序列化到JSON数组，并以单个HTTP响应将其发送回。

客户端等待此单个响应，但在此期间没有任何线程被阻塞。

如果您想要实现流式传输的效果，您需要利用不同的内容类型或底层协议，如WebSockets。签出以下关于application/stream+json内容类型的SO线程：Spring WebFlux Flux行为with non streaming application/json