return stripInvalidXMLCharacters(//
                value//
                        .replace("&", "&") //
                        .replace("<", "&lt;")//
                        .replace(">", "&gt;")//
                        .replace("\"", "&quot;")//
                        .replace("\'", "&apos;")//
        );
    }

    /**
     * Strips invalid XML characters from the input string.

    }

    public void test_doGet_dir() {
        final File file = ResourceUtil.getResourceAsFile("test");
        String path = file.getAbsolutePath();
        if (!path.startsWith("/")) {
            path = "/" + path.replace('\\', '/');
        }
        try {
            fsClient.doGet("file://" + path);
            fail();
        } catch (final ChildUrlsException e) {
            final Set<RequestData> urlSet = e.getChildUrlList();

     */
    protected String path;

    /**
     * A string to replace ?.
     */
    protected String questionStr = "_QUEST_";

    /**
     * A string to replace :.
     */
    protected String colonStr = "_CLN_";

    /**
     * A string to replace ;.
     */
    protected String semicolonStr = "_SCLN_";

    /**
     * A string to replace &.
     */
    protected String ampersandStr = "_AMP_";

        String input = content.replaceAll("[\\r\\n]", " ");
        if (ignoreCommentTag) {
            input = input.replaceAll("<!--[^>]+-->", "");
        } else {
            input = input.replace("<!--", "").replace("-->", "");
        }
        final Matcher matcher = getTagPattern().matcher(input);
        final StringBuffer sb = new StringBuffer();
        final Pattern attrPattern = Pattern.compile("\\s[^ ]+=\"([^\"]*)\"");

        final File targetFile = ResourceUtil.getResourceAsFile("test");
        String path = targetFile.getAbsolutePath();
        if (!path.startsWith("/")) {
            path = "/" + path.replace('\\', '/');
        }
        final String url = "file:" + path;

        final int maxCount = 3;
        final int numOfThread = 2;

        final File file = File.createTempFile("crawler-", "");

            final String text = source.get(FieldNames.TEXT).toString();
            if (skipDuplicateWords) {
                final String duplicateCheckStr = text.replace(" ", "");
                if (words.stream().map(word -> word.replace(" ", "")).anyMatch(word -> word.equals(duplicateCheckStr))) {
                    // skip duplicate word.
                    continue;
                }
            }

     * @param credentials The credentials.
     * @param value The value to replace.
     * @return The value with credentials replaced.
     */
    protected String replaceCredentials(final Credentials credentials, final String value) {
        if (StringUtil.isNotBlank(value)) {
            return value.replace(USERNAME, credentials.getUserPrincipal().getName()).replace(PASSWORD, credentials.getPassword());
        }

        final File targetFile = ResourceUtil.getResourceAsFile("test");
        String path = targetFile.getAbsolutePath();
        if (!path.startsWith("/")) {
            path = "/" + path.replace('\\', '/');
        }
        final String url = "file:" + path;

        final int maxCount = 3;
        final int numOfThread = 2;

        final File file = File.createTempFile("crawler-", "");

        } catch (final Exception e) {
            if (logger.isDebugEnabled()) {
                logger.debug("Failed to replace with new index.", e);
            }
            throw new SuggesterException("Failed to replace with new index.", e);
        }
    }

    /**
     * Switches the search alias to the current update index.
     */
    public void switchIndex() {

        String newPath = path.replace(".", "\\.").replace("?", "\\?").replace("*", ".*");
        if (newPath.charAt(0) != '/') {
            newPath = ".*" + newPath;
        }
        if (!newPath.endsWith("$") && !newPath.endsWith(".*")) {
            newPath = newPath + ".*";
        }
        return newPath.replace(".*.*", ".*");
    }

    /*
     * (non-Javadoc)
     *