NullPointerException in UndertowWebServer.destroy() when using @DirtiesContext and Citrus Spring Boot Simulator

[tschlat]

Description:
After upgrading from Spring Boot 3.5.7 to 3.5.8, tests using @DirtiesContext with Undertow as embedded server fail with a NullPointerException during context cleanup.

Affected versions:
Spring Boot 3.5.8 (works in 3.5.7)
Undertow 2.3.20.Final

Root Cause Analysis:
This appears to be a regression introduced by the fix for #48061 (backport of #47141). The separation of stop() and destroy() methods in UndertowWebServer causes DeploymentManagerImpl.stop() to be called when deployment is already null.

The following public project can be used to reproduce the issue:
https://github.com/tschlat/spring-boot-3-5-8-undertow-issue

[wilkinsona]

Thanks for reporting this and for the sample. Thankfully, I think the scope of this is limited to those who are using Citrus as its presence is what's triggering the double-close of the same context. org.citrusframework.CitrusSpringContext is registered as a bean so its close() method is called when the context is closed. It then makes a re-entrant call to org.springframework.context.ConfigurableApplicationContext.close(), resulting in Boot's DeploymentManagerHttpHandlerFactory.DeploymentManagerHandler.close() being called twice.