SpringBoot Kotlin Coroutines support for ApplicationRunner and CommandLineRunner

Like the coroutines repository added in the Spring Data and Coroutines Router DSL in the Spring framework. Add Coroutines support for ApplicationRunner and CommandLineRuner to accept suspend functions.

Currently I have to use a runBlocking to wrap my Kotlin Coroutines codes.

@Component
class SampleDataInitializer(val posts: PostRepository) : ApplicationRunner {
    override fun run(args: ApplicationArguments?) {
        runBlocking {
            posts.save(Post(title = "Sample Post", content = "Sample Content"))
        }
    }

}

// here PostRepository extends CoroutineCrudRepository

Hope simply remove the runBlocking{} like this.

@Component
class SampleDataInitializer(val posts: PostRepository) : CouroutineApplicationRunner {
    override suspend fun run(args: ApplicationArguments?) {
        posts.save(Post(title = "Sample Post", content = "Sample Content"))
    }
}

Comment From: wilkinsona

Thanks for the suggestion. Can you please provide some examples of when this support would be useful to you?

Comment From: hantsy

@wilkinsona Updated the original post.

Comment From: wilkinsona

Thanks but I'm afraid that I still don't see the benefit. Both ApplicationRunner and CommandLineRunner are synchronous contracts that are run in the order defined by their @Order annotation or Ordered implementation. You're proposing a new CoroutingApplicationRunner API. How would this work with other ApplicationRunner implementations ordered to run before or after the runner that's using a coroutine?

Comment From: hantsy

In the past months, I worked on a Spring WebFlux/R2dbc/Kotlin Coroutines project, but found a lot of Spring features still lack Coroutines support which are provided in the legacy project https://github.com/konrad-kaminski/spring-kotlin-coroutine, such as ApplicationEvent/EventListener, cache, schedule etc.

Spring 6.0.5 has just added a Coroutine variant CoWebFilter as alternative of WebFilter.

I just want my codes look more consistent when using Kotlin Coroutines. Maybe it is easier if Spring add Coroutines to Configurations/beans declarations.

Comment From: wilkinsona

Coroutines are a good fit for WebFilter which is already part of the Reactor-based WebFlux stack. As I explained above, I don't think they're a good fit for the ApplicationRunner and CommandLineRunner contract so I'm going to close this issue accordingly. Thanks anyway for the suggestion.