Javalin fails to start on latest Loom Early Access Build

Actual behavior (the bug)

Javalin fails to start when running on the latest Project Loom Early Access build.

Exception in thread "main" java.lang.NoSuchMethodException: java.util.concurrent.Executors.newVirtualThreadExecutor()
	at java.base/java.lang.Class.getMethod(Class.java:2259)
	at io.javalin.core.LoomUtil.getExecutorService(LoomUtil.kt:22)
	at io.javalin.jetty.LoomThreadPool.<init>(JettyUtil.kt:89)
	at io.javalin.jetty.JettyUtil.defaultThreadPool(JettyUtil.kt:28)
	at io.javalin.jetty.JettyUtil.getOrDefault(JettyUtil.kt:20)
	at io.javalin.jetty.JettyServer.server(JettyServer.kt:34)
	at io.javalin.Javalin.start(Javalin.java:179)
	at io.javalin.Javalin.start(Javalin.java:147)
	at Main.main(Main.java:6)

Expected behavior

Javalin starts normally.

To Reproduce

Run Javalin with the latest preview build 18-loom+5-274 http://jdk.java.net/loom/

Additional context

The getExecutorService function is referencing the old method name for getting an ExecutorService that utilizes virtual threads.

fun getExecutorService(): ExecutorService {
    if (!loomAvailable) {
        throw IllegalStateException("Your Java version (${System.getProperty("java.version")}) doesn't support Loom")
    }
    return Executors::class.java.getMethod("newVirtualThreadExecutor").invoke(Executors::class.java) as ExecutorService
}

It should be looking for newVirtualThreadPerTaskExecutor according to the latest docs:

https://download.java.net/java/early_access/loom/docs/api/java.base/java/util/concurrent/Executors.html

[tipsy]

@pkkummermo That seems like a bit too much effort for a preview feature, I’m happy with the merged PR.

[pkkummermo]

A quick fix during the preview timeline, would be to check on multiple methods and just check if one of them exists. If there’s no match, throw an Exception with a link to either this issue or the Javalin repo 😃

Edit: We could even toss in a .warn when you’re using an old preview build.