Illegal reflective access by org.springframework.cglib.core.ReflectUtils

[LifeIsStrange]

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.springframework.cglib.core.ReflectUtils (file:/home/stephane/.gradle/caches/modules-2/files-2.1/org.springframework/spring-core/5.3.2/152489ed8223a6ad19065a3cd1ee6b9e20c0b82f/spring-core-5.3.2.jar) to method java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain)
WARNING: Please consider reporting this to the maintainers of org.springframework.cglib.core.ReflectUtils
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

note: I also upgraded to gradle 6.8
I get this warning on server launch after having updated spring dependencies.

[LifeIsStrange]

The warning disappear if I comment // developmentOnly("org.springframework.boot:spring-boot-devtools")
why ?

[LifeIsStrange]

The doc https://docs.spring.io/spring-boot/docs/1.5.16.RELEASE/reference/html/using-boot-devtools.html#using-boot-devtools
says using compileOnly is best practice but I believe (?) it is obscolete and should be developmentOnly() ?
Anyway, both trigger the warning.
Can this trigger bugs ?
This should be fixed as it must affect a huge number of projects

[wilkinsona]

You've described the problem as a regression and that it is occurring after upgrading some Spring dependencies. What version were you using before and what version have you upgraded to?

The doc says using compileOnly is best practice but I believe (?) it is obscolete and should be developmentOnly() ?

That documentation is for Spring Boot 1.5.16 which predates the developmentOnly configuration. More recent documentation recommends the use of developmentOnly.

The warning disappear if I comment // developmentOnly("org.springframework.boot:spring-boot-devtools")
why ?

Using Devtools changes the class loaders that are involved. I can't say exactly why it is triggering the warning, but that is a likely cause. To be more precise, we'll need some more information about the problem. To that end, can you please provide a minimal sample that reproduces it? You can share it with us by zipping it up and attaching it to this issue or by pushing it to a separate repository on GitHub.

[LifeIsStrange]

Many thanks for the quick and correct answer, unfortunately I can't work on that until a few days, I'll ping you when I'll submit a reproducer.