public String format(String key, Object... params) {
        try {
            return String.format(resourceBundle.getString(messagePrefix + key), params);
        } catch (MissingResourceException e) {
            return '!' + key + '!';
        }
    }
Return the message <code>key</code> formatted with the given <code>params</code>.

@param key    the message key in the ResourceBundle
@param params the format arguments
@return the formatted String
plugins/url-whitelist-policy/src/main/java/io/apiman/plugins/urlwhitelist/util/Messages.java