In Struts 2, resource bundles can be associated with classes. The framework will automatically discover and load class-orientated resource bundles. You can also specify one or more global resource bundles, which would be available to all classes in the application, using either the standard properties file, or a custom listener.
Global resource bundles can be specified in the
struts.properties configuration file.
The framework searches the class heirarchy first, then, as a last resource, checks the global resources.
Multiple resource bundles can be specified by providing a comma-separated list.
Aside from the properties file, a Listener could also be used to load global resource bundles.
(under listeners section)