Spring MVC coroutine example

CoroutineNetworkRequestController.kt

@RestController
@RequestMapping("/requests")
class CoroutineNetworkRequestController {

    private val url = "https://en.wikipedia.org/api/rest_v1/page/summary"
    private val logger = LogManager.getLogger(CoroutineNetworkRequestController::class.java)

    /**
     * do request with async and awaitAll
     */
    @GetMapping("/async")
    suspend fun requestAsync(): List<String?> {
        logger.info("Request with async...")
        var result: List<String?>
        val time = measureTimeMillis {
            coroutineScope {
                val java = async { get("$url/Java") }
                val kotlin = async { get("$url/Kotlin") }
                logger.info("Waiting for results...")

                result = awaitAll(java, kotlin)
                logger.info("Results received!")
            }
        }
        logger.info("Time: $time") // less than 2000ms
        return result
    }

    /**
     * do request without async and awaitAll
     */
    @GetMapping
    suspend fun request(): List<String?> {
        logger.info("Request with sequential execution...")
        var result: List<String?>
        val time = measureTimeMillis {
            val java = get("$url/Java")
            val kotlin = get("$url/Kotlin")
            logger.info("Waiting for results...")

            result = listOf(java, kotlin)
            logger.info("Results received!")
        }
        logger.info("Time: $time") // more than 2000ms
        return result
    }

    private suspend fun get(url: String): String? {
        logger.info("Requesting $url...")
        delay(1000L)
        return withContext(Dispatchers.IO) {
            RestTemplate().getForObject(url, String::class.java)
        }
    }
}