public String format(String key, Object ... params) {
        ResourceBundle bundle = getBundle(clazz.getName());
        if (bundle.containsKey(key)) {
            String msg = bundle.getString(key);
            return MessageFormat.format(msg, params);
        } else {
            return MessageFormat.format("!!{0}!!", key);
        }
    }
Look up a message in the i18n resource message bundle by key, then format the
message with the given params and return the result.
@param key the key
@param params the parameters
@return formatted string
common/util/src/main/java/io/apiman/common/util/AbstractMessages.java