Could not initialize class org.xnio.channels.Channels

[MichaelJHaywood]

I can successfully build and execute keycloak-extension-playground but when accessing http://localhost:8081/auth an exception is thrown.

I'm using Java 11.0.15. I've ran mvn install on my Keycloak 18.0.0 project successfully and also the keycloak-admin-ui admin-theme with 18.0.0. This is Windows 10.

I've tried using Java 11.0.14 as there are mentions of 11.0.15 causing errors like this.

I can't see what I've missed in the instructions.

What could be causing this?

16:03:58,110 ERROR XNIO-1 task-1 [io.undertow.request] UT005071: Undertow request failed HttpServerExchange{ GET /auth}
java.io.IOError: java.io.FileNotFoundException: Invalid file path
	at org.xnio.channels.Channels$4.run(Channels.java:1103)
	at org.xnio.channels.Channels$4.run(Channels.java:1093)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at org.xnio.channels.Channels.<clinit>(Channels.java:1093)
	at io.undertow.servlet.spec.ServletOutputStreamImpl.close(ServletOutputStreamImpl.java:628)
	at io.undertow.servlet.spec.HttpServletResponseImpl.closeStreamAndWriter(HttpServletResponseImpl.java:498)
	at io.undertow.servlet.spec.HttpServletResponseImpl.responseDone(HttpServletResponseImpl.java:587)
	at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:334)
	at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:79)
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:134)
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:131)
	at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
	at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:255)
	at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:79)
	at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:100)
	at io.undertow.server.Connectors.executeRootHandler(Connectors.java:387)
	at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:852)
	at org.jboss.threads.ContextClassLoaderSavingRunnable.run(ContextClassLoaderSavingRunnable.java:35)
	at org.jboss.threads.EnhancedQueueExecutor.safeRun(EnhancedQueueExecutor.java:1982)
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1486)
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1348)
	at org.xnio.XnioWorker$WorkerThreadFactory$1$1.run(XnioWorker.java:1280)
	at java.base/java.lang.Thread.run(Thread.java:829)
Caused by: java.io.FileNotFoundException: Invalid file path
	at java.base/java.io.FileOutputStream.<init>(FileOutputStream.java:231)
	at java.base/java.io.FileOutputStream.<init>(FileOutputStream.java:126)
	at org.xnio.channels.Channels$4.run(Channels.java:1098)
	... 23 more
16:03:59,355 ERROR XNIO-1 task-1 [io.undertow.request] UT005071: Undertow request failed HttpServerExchange{ GET /auth}
java.lang.NoClassDefFoundError: Could not initialize class org.xnio.channels.Channels
	at io.undertow.servlet.spec.ServletOutputStreamImpl.close(ServletOutputStreamImpl.java:628)
	at io.undertow.servlet.spec.HttpServletResponseImpl.closeStreamAndWriter(HttpServletResponseImpl.java:498)
	at io.undertow.servlet.spec.HttpServletResponseImpl.responseDone(HttpServletResponseImpl.java:587)
	at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:334)
	at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:79)
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:134)
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:131)
	at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
	at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:255)
	at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:79)
	at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:100)
	at io.undertow.server.Connectors.executeRootHandler(Connectors.java:387)
	at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:852)
	at org.jboss.threads.ContextClassLoaderSavingRunnable.run(ContextClassLoaderSavingRunnable.java:35)
	at org.jboss.threads.EnhancedQueueExecutor.safeRun(EnhancedQueueExecutor.java:1982)
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1486)
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1377)
	at org.xnio.XnioWorker$WorkerThreadFactory$1$1.run(XnioWorker.java:1280)
	at java.base/java.lang.Thread.run(Thread.java:829)