The translation properties files must exist in the same directory structure as the interface. The name of the properties file InterfaceName.i18n_language_country_variant.properties. For example if you have a class named org.jboss.logging.tools.examples.ErrorMessages and you want to translate this into French you create a properties file called ErrorMessages.i18n_fr.properties in a directory org/jboss/logging/tools/examples.