Classloading issues with CustomResource

[iocanel]

From: quarkusio/quarkus#15250

2021-02-22 21:07:28,941 ERROR [io.qua.run.Application] (Quarkus Main Thread) Failed to start application (with profile dev): java.lang.ClassNotFoundException: io.websitecd.operator.crd.WebsiteSpec
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
	at io.quarkus.bootstrap.classloading.QuarkusClassLoader.loadClass(QuarkusClassLoader.java:428)
	at io.quarkus.bootstrap.classloading.QuarkusClassLoader.loadClass(QuarkusClassLoader.java:378)
	at java.base/java.lang.Class.forName0(Native Method)
	at java.base/java.lang.Class.forName(Class.java:315)
	at io.fabric8.kubernetes.client.CustomResource.getInstantiator(CustomResource.java:309)
	at io.fabric8.kubernetes.client.CustomResource.genericInit(CustomResource.java:337)
	at io.fabric8.kubernetes.client.CustomResource.initSpec(CustomResource.java:117)
	at io.fabric8.kubernetes.client.CustomResource.<init>(CustomResource.java:108)
	at io.websitecd.operator.crd.Website.<init>(Website.java:20)

The problem here seems to be that we make the assumption that TCCL will be responsible to load the class.

How to solve this

• Since we can really know which classloader may or may not load the class, our safest bet is to use getClass().getClassLoader().
• Why?
• Because, most of the time spec/status classes will be either in the same artifact (or a dependency) of the artifact containing the enclosing class.
  So, the classloader that loaded the enclosing class most of the time should be able to also load the spec and status. That should even work in environments like OSGi.

In addition to that we should use TCCL as a fallback mechanism.