* @param extractor The extractor to add. Must not be null.
     */
    public void addExtractor(final String key, final Extractor extractor) {
        if (StringUtil.isBlank(key)) {
            throw new CrawlerSystemException("The key is null.");
        }
        if (extractor == null) {
            throw new CrawlerSystemException("The extractor is null.");
        }

                    groupId, artifactId, getVersion(), type, "The version cannot be empty.");
        }
    }

    public static boolean empty(String value) {
        return value == null || value.isBlank();
    }

    @Override
    public String getClassifier() {
        return classifier;
    }

    @Override
    public boolean hasClassifier() {

            crawler.setSessionId(sid);
            sessionIdList.add(sid);

            final String urlsStr = webConfig.getUrls();
            if (StringUtil.isBlank(urlsStr)) {
                logger.warn("No target urls. Skipped");
                break;
            }

            // interval time
            final int intervalTime =

            } else {
                this.queryString = queryString;
            }
        } else {
            this.queryString = queryString;
        }
        if (StringUtil.isBlank(this.queryString)) {
            this.queryString = "*";
        }
        if (isQuery) {
            LaRequestUtil.getOptionalRequest().ifPresent(request -> {
                highlightedQuerySet = new HashSet<>();

            if ("field".equals(qName)) {
                fieldName = attributes.getValue("name");
                if (StringUtil.isBlank(fieldName)) {
                    fieldName = null;
                }
                buffer.setLength(0);
            } else if ("list".equals(qName)) {

     * If the surname is blank, it will be set to the user's name.
     *
     * @param user the user entity to store
     */
    public void store(final User user) {
        if (StringUtil.isBlank(user.getSurname())) {
            user.setSurname(user.getName());
        }

        ComponentUtil.getAuthenticationManager().insert(user);

        userBhv.insertOrUpdate(user, op -> {

        return split(text, "\n")
                .get(stream -> stream.map(String::trim).filter(StringUtil::isNotBlank).map(this::getFilterPath).filter(s -> {
                    if (StringUtil.isBlank(s)) {
                        return false;
                    }
                    if (Arrays.stream(webProtocols).anyMatch(p -> s.startsWith(p))) {
                        return web;
                    }

    protected boolean isEmptyArray(final String[] values) {
        if (values == null || values.length == 0) {
            return true;
        }
        return stream(values).get(stream -> stream.allMatch(StringUtil::isBlank));
    }

    /**
     * Simplifies the array.
     *
     * @param values The array.
     * @return The simplified array.
     */
    protected static String[] simplifyArray(final String[] values) {

        final String loginUrl = replaceCredentials(credentials, originalLoginUrl);
        final String loginReqParams = replaceCredentials(credentials, getParameter(LOGIN_PARAMETERS));

        if (StringUtil.isBlank(loginUrl)) {
            if (logger.isDebugEnabled()) {
                logger.debug("No login.url");
            }
            return;
        }

        final HttpUriRequest httpRequest;

                if (resultsPerPage instanceof Integer) {
                    form.num = (Integer) resultsPerPage;
                }
            }
        }

        if (StringUtil.isBlank(form.q) && form.fields.isEmpty() && !form.hasConditionQuery()) {
            // redirect to index page
            form.q = null;
            return redirectToRoot();
        }

        try {