Disable some of Tomcat's reference clearing to avoid warnings on Java 11

[casper5822]

Spring boot 2.1.0 GA
Oracle JDK 11
STS 4.0.1

Hello,
when i run the project in STS and i stop the execution there are this warnings:

This in STS 4.0.1 :

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.catalina.loader.WebappClassLoaderBase (file:/<home_path>/.m2/repository/org/apache/tomcat/embed/tomcat-embed-core/9.0.12/tomcat-embed-core-9.0.12.jar) to field java.io.ObjectStreamClass$Caches.localDescs
WARNING: Please consider reporting this to the maintainers of org.apache.catalina.loader.WebappClassLoaderBase
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

Thank for your help.

[wilkinsona]

Thanks for the report, but the Spring Boot team are not the maintainers of org.apache.catalina.loader.WebappClassLoaderBase. That class is maintained by the Tomcat team and their position is that the benefit of accessing localDescs outweighs the cost of the warning being generated during shutdown.

[philwebb]

I was just typing the same thing :) FYI, this is the code in question.

[wilkinsona]

On second thoughts, we should at least consider disabling the check. I believe we can do so by calling org.apache.catalina.loader.WebappClassLoaderBase.setClearReferencesObjectStreamClassCaches(boolean) as part of creating and configuring our TomcatEmbeddedWebappClassLoader.