if ("fess_config".equals(index)) {
                    index = fessConfig.getIndexConfigIndex();
                } else if ("fess_user".equals(index)) {
                    index = fessConfig.getIndexUserIndex();
                } else if ("fess_basic_config".equals(index) && !"fess_config".equals(fessConfig.getIndexConfigIndex())) {
                    index = "basic_" + fessConfig.getIndexConfigIndex();
                }

            final String userIndex = fessConfig.getIndexUserIndex() + ".user";
            Arrays.stream(FileUtil.readUTF8(dataPath).split("\n"))
                    .map(line -> line//
                            .replace("\"_index\":\"fess_config.", "\"_index\":\"" + fessConfig.getIndexConfigIndex() + ".")//
                            .replace("\"_index\":\"fess_user.", "\"_index\":\"" + fessConfig.getIndexUserIndex() + ".")//

     * The value is, e.g. fess_user <br>
     * comment: Index name for user data.
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getIndexUserIndex();

    /**
     * Get the value for the key 'index.log.index'. <br>
     * The value is, e.g. fess_log <br>
     * comment: Index name for log data.