Hello. Can I declare suspending methods in Spring ...

# spring

[Robert Jaros]

Hello. Can I declare suspending methods in Spring components in the current Spring Boot version (2.1.6)?

[sdeleuze]

No, only in Spring Boot 2.2 with WebFlux

[Robert Jaros]

And in 2.2 but without webflux I can't?

[sdeleuze]

Nope, Coroutines support is built on top of WebFlux, see https://spring.io/blog/2019/04/12/going-reactive-with-spring-coroutines-and-kotlin-flow for more details.

[Robert Jaros]

I'm using 2.1.6 with some non-typical configuration (SOAP services with Apache CXF). I've tested coroutines and they seem to work for me. So I'm puzzled.

[Robert Jaros]

how can it work? 🙂

[Robert Jaros]

I've created a component like this:

@Service
class DokumentService {

    suspend fun test() {
        println("pre test")
        delay(5000)
        println("post test")
    }
}

[sdeleuze]

Where/how are you using this service ?

[Robert Jaros]

And I have a web service component (initialized by CXF):

@Service
@WebService(...)
class PeupImpl(
    private val dokumentService: DokumentService
) : Peup, CoroutineScope by CoroutineScope(Dispatchers.Default) {

    override fun oczekujaceDokumentyAsync(
        request: OczekujaceDokumentyRequestType,
        asyncHandler: AsyncHandler<OczekujaceDokumentyResponseType>
    ): Future<*> {
        return asyncWS(asyncHandler) {
            dokumentService.test()
            delay(10000)
            OczekujaceDokumentyResponseType().apply { liczba = 2 }
        }
    }

}

[Robert Jaros]

asyncWs is a helper extension function:

fun <T> CoroutineScope.asyncWS(asyncHandler: AsyncHandler<T>, block: suspend () -> T): ServerAsyncResponse<T> {
    val result = ServerAsyncResponse<T>()
    launch {
        val v = block()
        result.set(v)
        asyncHandler.handleResponse(result)
    }
    return result
}

[Robert Jaros]

This is just some of my testing, to find out if I can use coroutines for soap web services. It seems to work, but I'm not sure if I'm not missing something about Spring Boot.

[Robert Jaros]

a service should be a proxy, right?

[Robert Jaros]

is it just proxying suspending function?

[sdeleuze]

Service does not imply proxy

[sdeleuze]

Here you are not using any kind of Coroutines support from Spring since you are creating the coroutines scope yourself

[sdeleuze]

I have not tried this kind of construct

[Robert Jaros]

when a service is injected as a proxy and when it's not?

[sdeleuze]

It depends if you need transactions, security, etc.

[sdeleuze]

Spring Boot 2.1 has 0 support for Coroutines so pretty sure that will fail for some use cases

[Robert Jaros]

And what is the state of 2.2? When it will be production ready?

[sdeleuze]

https://github.com/spring-projects/spring-boot/milestone/145

[sdeleuze]

Currently CoroutineScope by CoroutineScope usage pattern is not actively supported to feel free to create an issue at Spring Framework level if you see some issues.

[Robert Jaros]

ok, thx for help! 🙂