UndertowWebServerFactoryCustomizer requires commons lang via an unintended import on ClassUtils

[ionelmanolache]

Hi,

I use Undertow and after upgraded to v2.3.3, app failed to start with error NoClassDefFoundError;org.apache.commons.lang.ClassUtils in 'UndertowWebServerFactoryCustomizer'
(see commit log f0d9002)

file https://github.com/spring-projects/spring-boot/commits/master/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/embedded/UndertowWebServerFactoryCustomizer.java

Thank you and best regards,
Ionel.

[snicoll]

Oops, thank you very much for the report. We meant to import ClassUtils from the core framework there.

[wilkinsona]

This needs to be fixed in 2.2.x too. Thankfully we haven't released that one yet.

[snicoll]

The import should have been prevented by a Checkstyle rule. Unfortunately it doesn't work as expected, I've created a separate issue to revisit it (#23062)