These features require Java 6 or higher due to their dependency on the ResourceBundle.Control class. To some degree, ResourceBundleMessageSource catches up with ReloadableResourceBundleMessageSource now. However, as noted in the javadoc, there are still severe limitations in the standard ResourceBundle class that justify an ongoing investment in our own ReloadableResourceBundleMessageSource (based on the Spring resource abstraction, with manual parsing of properties files).
Issue: SPR-7392