spring 6 http interface

spring 6 에서 feign과 유사한 http interface가 추가된 것으로 확인되었습니다.

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https://www.baeldung.com/spring-6-http-interface

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최근, spring을 kotlin을 이용하여 reactive하게 작성하는 방법을 알게되서 coroutine을 적용해서 작성했는데, 다음과 같은 이슈가 발생하였습니다.

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class org.springframework.http.ResponseEntity cannot be cast to class reactor.core.publisher.Mono (org.springframework.http.ResponseEntity and reactor.core.publisher.Mono are in unnamed module of loader 'app')

class httpClient { @GetExchange("path") suspend fun call() : ResponseEntity }

이런 형태로 작성했을 때 문제는 class casting exception이 발생된다.

class org.springframework.http.ResponseEntity cannot be cast to class reactor.core.publisher.Mono (org.springframework.http.ResponseEntity and reactor.core.publisher.Mono are in unnamed module of loader 'app')

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그리고 suspend를 제거할 경우 아래와 같은 에러가 발생된다.

java.lang.IllegalStateException: block()/blockFirst()/blockLast() are blocking, which is not supported in thread reactor-http-nio-3 at reactor.core.publisher.BlockingSingleSubscriber.blockingGet(BlockingSingleSubscriber.java:117) ~[reactor-core-3.5.3.jar:3.5.3] Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: Error has been observed at the following site(s): ...

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그래서 수정하는 방법은 다음과 같다. http interface는 coroutine을 지원하지 않기 때문에 suspend 선언을 제거하고, 호출하는 곳에서 awaitSingle을 이용하여 처리하는 것이다.

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class httpClient { @GetExchange("path") fun call() : Mono> } @Service class Service(private val httpClient:HttpClient) { fun call() { httpClient.call().awaitSingle() // business logic.. } }

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처음하는거라 제대로 알지 못했고, 지원하는지 여부 부터 조사하고 적용했었어야 했는데, 이렇게 또 배운다.

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https://spring.io/blog/2019/04/12/going-reactive-with-spring-coroutines-and-kotlin-flow

Going Reactive with Spring, Coroutines and Kotlin Flow

Level up your Java code and explore what Spring can do for you.

// 24.02.21 추가

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예제도 잘 작성되어 있는 Bealdung

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https://www.baeldung.com/spring-6-http-interface

[**HTTP Interface in Spring 6

Baeldung**](https://www.baeldung.com/spring-6-http-interface)

Spring has a new web client builder that’s similar to OpenFeign, but is native to Spring. We look at how to build API clients with itm .

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