/** The key of the configuration. e.g. text/html=X-XSS-Protection: 1; mode=block<br>
     * text/html=Content-Security-Policy: reflected-xss block<br>
     * text/html=X-Frame-Options: SAMEORIGIN<br>
     *  */
    String RESPONSE_HEADERS = "response.headers";

    /** The key of the configuration. e.g. fess.search */
    String INDEX_DOCUMENT_SEARCH_INDEX = "index.document.search.index";