NPE in new QuarkusExceptionHandler

[FroMage]

Just got that for an async jaxrs exception:

Jun 04, 2019 11:25:49 AM io.quarkus.undertow.runtime.QuarkusExceptionHandler handleThrowable
ERROR: Exception handling request dbe37070-88d5-4cda-b7a1-e41998dcc160-1 to /@QuarkusError
java.lang.RuntimeException: java.lang.NullPointerException
	at io.undertow.servlet.spec.RequestDispatcherImpl.error(RequestDispatcherImpl.java:508)
	at io.undertow.servlet.spec.RequestDispatcherImpl.error(RequestDispatcherImpl.java:420)
	at io.undertow.servlet.spec.HttpServletResponseImpl.doErrorDispatch(HttpServletResponseImpl.java:164)
	at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:299)
	at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:81)
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:138)
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:135)
	at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
	at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
	at io.quarkus.undertow.runtime.UndertowDeploymentTemplate$7$1$1.call(UndertowDeploymentTemplate.java:485)
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:272)
	at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
	at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:104)
	at io.undertow.server.Connectors.executeRootHandler(Connectors.java:364)
	at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:830)
	at org.jboss.threads.ContextClassLoaderSavingRunnable.run(ContextClassLoaderSavingRunnable.java:35)
	at org.jboss.threads.EnhancedQueueExecutor.safeRun(EnhancedQueueExecutor.java:2011)
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1538)
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1395)
	at org.jboss.threads.DelegatingRunnable.run(DelegatingRunnable.java:29)
	at org.jboss.threads.ThreadLocalResettingRunnable.run(ThreadLocalResettingRunnable.java:32)
	at java.lang.Thread.run(Thread.java:748)
	at org.jboss.threads.JBossThread.run(JBossThread.java:479)
Caused by: java.lang.NullPointerException
	at io.quarkus.undertow.runtime.QuarkusErrorServlet.generateHeaderMessage(QuarkusErrorServlet.java:134)
	at io.quarkus.undertow.runtime.QuarkusErrorServlet.doGet(QuarkusErrorServlet.java:114)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:686)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:791)
	at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:74)
	at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
	at io.undertow.servlet.handlers.ServletChain$1.handleRequest(ServletChain.java:68)
	at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
	at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
	at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:274)
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchToPath(ServletInitialHandler.java:209)
	at io.undertow.servlet.spec.RequestDispatcherImpl.error(RequestDispatcherImpl.java:502)
	... 22 more

I can work around it by checking if the exception is null, but I don't quite understand why it's null and where it's actually set.

@stuartwdouglas ?

[stuartwdouglas]

So the issue is that this is implemented by mapping a 500 error page handler, but it is possible for the application to just directly dispatch a 500 error with no associated exception, which is what is happening here.