public static String getMultString(String... keys) {
        Map<String, String> map = new HashMap<String, String>();

        Properties prop = loadI18nProp();
        if (keys!=null && keys.length>0) {
            for (String key: keys) {
                map.put(key, prop.getProperty(key));
            }
        } else {
            for (String key: prop.stringPropertyNames()) {
                map.put(key, prop.getProperty(key));
            }
        }

        String json = JacksonUtil.writeValueAsString(map);
        return json;
    }
get mult val of i18n mult key, as json

@param keys
@return
larkmidtable-web/larkmt-admin/src/main/java/com/larkmt/cn/admin/core/util/I18nUtil.java