Created
June 3, 2021 07:44
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A Kotlin Coroutine snippet trying to simulate what happens in Spring WebFlux
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import kotlinx.coroutines.Dispatchers | |
import kotlinx.coroutines.runBlocking | |
import kotlinx.coroutines.withContext | |
import java.util.concurrent.Executor | |
import java.util.concurrent.Executors | |
import kotlin.coroutines.suspendCoroutine | |
// Simulate what may happen in Spring WebFlux, where a Spring call your functions in their executors | |
suspend fun resumeOnSpecificJavaExecutor(javaExecutor: Executor) = suspendCoroutine<Int> { | |
javaExecutor.execute { it.resumeWith(Result.success(1)) } | |
} | |
fun main() { | |
// Make the single thread executor that is outside the main thread, and print its thread id | |
val executor = Executors.newSingleThreadExecutor() | |
executor.execute { println("Inside the Thread Executor, Thread Id ${Thread.currentThread().id}") } | |
// Use the Unconfined, it would be executed on the main thread (Id = 1), then either resumed | |
// on the same thread, or will be resumed on the specific executor that is made in the previous step | |
runBlocking { | |
withContext(Dispatchers.Unconfined) | |
{ | |
println("Coroutine, Thread Id ${Thread.currentThread().id}") | |
val result = resumeOnSpecificJavaExecutor(executor) | |
println("Coroutine, Thread Id ${Thread.currentThread().id}, Result is ${result}") | |
} | |
} | |
// Use IO dispatcher, which executes and resumes the coroutine on a thread pool allocated by Kotlin | |
runBlocking { | |
withContext(Dispatchers.IO) | |
{ | |
println("Coroutine, Thread Id ${Thread.currentThread().id}") | |
val result = resumeOnSpecificJavaExecutor(executor) | |
println("Coroutine, Thread Id ${Thread.currentThread().id}, Result is ${result}") | |
} | |
} | |
executor.shutdown() | |
} |
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