Previously, BeanDefinitionLoader declared a field of type
GroovyBeanDefinitionReader which is a GroovyObject subclass. This is
problematic as BeanDefinitionLoader is always loaded but Groovy is an
optional dependency. Even on a JVM where class verification is performed
lazily, this can still cause problems if something reflectively tries
to access the class’s declared fields. On a JVM where classes are
verified at load time, it would be impossible to start a Spring Boot
application without having Groovy on the classpath.
This commit changes the field to be a BeanDefinitionReader, removing
the indirect reference to GroovyObject form BeanDefinitionLoader’s
signature. The reader is downcast to a GroovyBeanDefinitionReader in the
body of a method body that will only be invoked when Groovy is on the
classpath.
Closes gh-5040
c0a2c88da1