spring webflux返回application/stream+json
2018-02-08 00:00
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序
本文主要研究下spring webflux返回application/stream+json的实例maven
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-webflux</artifactId> </dependency>
controller
/** * curl -i localhost:8080/stream * @return */ @GetMapping(value = "/stream",produces = MediaType.APPLICATION_STREAM_JSON_VALUE) public Flux<Price> priceStream(){ return Flux.interval(Duration.ofMillis(500)) .map(l -> new Price(System.currentTimeMillis(),ThreadLocalRandom.current().nextInt(100, 125))) .log(); }
注意这里produces = MediaType.APPLICATION_STREAM_JSON_VALUE
如果不是application/stream+json则调用端无法滚动得到结果,将一直阻塞等待数据流结束或超时。
输出
后台输出2018-02-08 21:36:49.701 INFO 1270 --- [ctor-http-nio-2] reactor.Flux.Map.1 : onSubscribe(FluxMap.MapSubscriber) 2018-02-08 21:36:49.702 INFO 1270 --- [ctor-http-nio-2] reactor.Flux.Map.1 : request(1) 2018-02-08 21:36:50.208 INFO 1270 --- [ parallel-2] reactor.Flux.Map.1 : onNext(Price(timestamp=1518097010208, value=120.0)) 2018-02-08 21:36:50.229 INFO 1270 --- [ctor-http-nio-2] reactor.Flux.Map.1 : request(31) 2018-02-08 21:36:50.708 INFO 1270 --- [ parallel-2] reactor.Flux.Map.1 : onNext(Price(timestamp=1518097010708, value=124.0)) 2018-02-08 21:36:51.208 INFO 1270 --- [ parallel-2] reactor.Flux.Map.1 : onNext(Price(timestamp=1518097011208, value=119.0)) 2018-02-08 21:36:51.707 INFO 1270 --- [ parallel-2] reactor.Flux.Map.1 : onNext(Price(timestamp=1518097011707, value=120.0)) 2018-02-08 21:36:52.207 INFO 1270 --- [ parallel-2] reactor.Flux.Map.1 : onNext(Price(timestamp=1518097012207, value=109.0)) 2018-02-08 21:36:52.707 INFO 1270 --- [ parallel-2] reactor.Flux.Map.1 : onNext(Price(timestamp=1518097012707, value=101.0)) 2018-02-08 21:36:53.208 INFO 1270 --- [ parallel-2] reactor.Flux.Map.1 : onNext(Price(timestamp=1518097013208, value=114.0)) 2018-02-08 21:36:53.707 INFO 1270 --- [ parallel-2] reactor.Flux.Map.1 : onNext(Price(timestamp=1518097013707, value=113.0)) 2018-02-08 21:36:54.206 INFO 1270 --- [ parallel-2] reactor.Flux.Map.1 : onNext(Price(timestamp=1518097014206, value=105.0)) 2018-02-08 21:36:54.708 INFO 1270 --- [ parallel-2] reactor.Flux.Map.1 : onNext(Price(timestamp=1518097014708, value=103.0)) 2018-02-08 21:36:55.208 INFO 1270 --- [ parallel-2] reactor.Flux.Map.1 : onNext(Price(timestamp=1518097015207, value=123.0)) 2018-02-08 21:36:55.212 INFO 1270 --- [ctor-http-nio-2] reactor.Flux.Map.1 : cancel()
调用端输出
curl -i localhost:8080/stream HTTP/1.1 200 OK transfer-encoding: chunked Content-Type: application/stream+json;charset=UTF-8 {"timestamp":1518097010208,"value":120.0} {"timestamp":1518097010708,"value":124.0} {"timestamp":1518097011208,"value":119.0} {"timestamp":1518097011707,"value":120.0} {"timestamp":1518097012207,"value":109.0} {"timestamp":1518097012707,"value":101.0} {"timestamp":1518097013208,"value":114.0} {"timestamp": 3fe8 1518097013707,"value":113.0} {"timestamp":1518097014206,"value":105.0} ^C
可以看到由于使用了application/stream+json,返回的transfer-encoding是chunked,因此调用端可以做到滚动输出。
分页
使用了webflux之后,可能好奇之前的分页调用怎么办。reactive-streams是把数据当做数据流来用的,因此spring data reactive并不支持返回Page,但是调用参数可以传Pageable参数public interface StocDao extends ReactiveCrudRepository<Stock, String> { Flux<Stock> findByName(String name,Pageable pageable); }
注意这里返回Flux<Stock>,而不是Page<Stock>
也就是相当于丢失了total count
小结
对于webflux返回的Flux的流数据,需要配合返回MediaType.APPLICATION_STREAM_JSON_VALUE,同时调用端也需要能够支持这种mediaType(WebClient支持),这样才能启到reactive streams的效果。
doc
Serving large datasets with Spring WebFluxmongo.reactive.repositories.usage
Is there any way to implement pagination in spring webflux and spring data reactive
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