Register environment in all bean factories in a hierarchy

Prior to this change, AbstractApplicationContext#prepareBeanFactory
registered a bean named 'environment' once and only once within a given
ApplicationContext hierarchy. This worked fine with the expectation
that the Environment object is always delegated downward to children of
that hierarchy. However, with SPR-9444 and the introduction of
ConfigurableEnvironment#merge, this expectation was violated; each
member of an application context hierarchy now maintains its own
distinct Environment instance, which means that by extension that each
application context's underlying BeanFactory should have its own
'environment' bean pointing to that context's environment instance.

This problem could manifest in getting the wrong environment instance
when calling #getBean(Environment) or when @Autowiring an Environment
instance, for example into a @Configuration class. As reported in
SPR-9756, this could result in false negative property lookups or
incorrect results when checking whether a profile is active.

This commit ensures that every bean factory in an application
hierarchy has an 'environment' bean referring to the object returned
from the enclosing ApplicationContext#getEnvironment method.

Issue: SPR-9756, SPR-9444

spring-context/src/main/java/org/springframework/context/support/AbstractApplicationContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2010 the original author or authors.
+ * Copyright 2002-2012 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -566,7 +566,7 @@ public abstract class AbstractApplicationContext extends DefaultResourceLoader
 		}
 
 		// Register default environment beans.
-		if (!beanFactory.containsBean(ENVIRONMENT_BEAN_NAME)) {
+		if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
 			beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
 		}