Prior to this change, any instantiation of an
AnnotationConfigApplicationContext would trigger the creation of three
StandardEnvironment objects: one for the ApplicationContext, one for the
AnnotatedBeanDefinitionReader, and one for the
ClassPathBeanDefinitionScanner.
The latter two are immediately swapped out when the ApplicationContext
delegates its environment to these subordinate objects anyway. Not only
is it inefficient to create these two extra Environments, it creates
confusion when debug-level logging is turned on. From the user's
perspective and in practice, there is only one Environment; logging
should reflect that.
This change ensures that only one Environment object is ever created for
a given ApplicationContext. If an AnnotatedBeanDefinitionReader or
ClassPathBeanDefinitionScanner are used in isolation, e.g. against a
plain BeanFactory/BeanDefinitionRegistry, then they will still create
their own local StandardEnvironment object.
All public API compatibility is preserved; new constructors have been
added where necessary to accommodate passing an Environment directly
to ABDR ar CPBDS.
Chris Beams