CompletionStage results in NPE

[dansiviter]

Environment Details

• Helidon Version: 2.2.2
• Helidon SE or Helidon MP: MP
• JDK version: 11
• OS: Windows
• Docker version (if applicable): N/A

---

Problem Description

If you use a CompletionStage as a response it results in a NPE:

Apr 04, 2021 7:09:57 PM io.helidon.webserver.RequestRouting$RoutedRequest defaultHandler
WARNING: Default error handler: Unhandled exception encountered.
java.util.concurrent.ExecutionException: Unhandled 'cause' of this exception encountered.
        at io.helidon.webserver.RequestRouting$RoutedRequest.defaultHandler(RequestRouting.java:397)
        at io.helidon.webserver.RequestRouting$RoutedRequest.nextNoCheck(RequestRouting.java:377)
        at io.helidon.webserver.RequestRouting$RoutedRequest.next(RequestRouting.java:420)
        at io.helidon.webserver.jersey.ResponseWriter.failure(ResponseWriter.java:172)
        at org.glassfish.jersey.server.ServerRuntime$Responder.process(ServerRuntime.java:438)
        at org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:263)
        at org.glassfish.jersey.internal.Errors$1.call(Errors.java:248)
        at org.glassfish.jersey.internal.Errors$1.call(Errors.java:244)
        at org.glassfish.jersey.internal.Errors.process(Errors.java:292)
        at org.glassfish.jersey.internal.Errors.process(Errors.java:274)
        at org.glassfish.jersey.internal.Errors.process(Errors.java:244)
        at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:265)
        at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:234)
        at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:680)
        at io.helidon.webserver.jersey.JerseySupport$JerseyHandler.lambda$doAccept$3(JerseySupport.java:293)
        at io.helidon.common.context.Contexts.runInContext(Contexts.java:117)
        at io.helidon.common.context.ContextAwareExecutorImpl.lambda$wrap$5(ContextAwareExecutorImpl.java:154)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
        at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: java.lang.NullPointerException
        at org.glassfish.jersey.internal.PropertiesResolver$1.resolveProperty(PropertiesResolver.java:88)
        at org.glassfish.jersey.internal.PropertiesResolver$1.resolveProperty(PropertiesResolver.java:83)
        at org.glassfish.jersey.server.ContainerRequest.resolveProperty(ContainerRequest.java:292)
        at org.glassfish.jersey.server.model.ResourceMethodInvoker.unwrapInvocableResponseType(ResourceMethodInvoker.java:489)  
        at org.glassfish.jersey.server.model.ResourceMethodInvoker.lambda$invoke$2(ResourceMethodInvoker.java:468)
        at org.glassfish.jersey.process.internal.Stages$LinkedStage.apply(Stages.java:284)
        at org.glassfish.jersey.process.internal.Stages.process(Stages.java:147)
        at org.glassfish.jersey.server.ServerRuntime$Responder.processResponse(ServerRuntime.java:371)
        at org.glassfish.jersey.server.ServerRuntime$Responder.process(ServerRuntime.java:363)
        at org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:258)
        ... 14 more

Steps to reproduce

1. Use helidon-mp-quickstart
2. Create a resource that responds with CompletionStage:

	@GET
	@Path("foo")
	@Produces(MediaType.TEXT_PLAIN)
	public CompletionStage<String> foo() {
		return CompletableFuture.completedStage("bar");
	}

[dansiviter]

@danielkec Thanks for quick fix!

[danielkec]

@dansiviter Thx for reporting! 🙇