logger.warn("Malformed URL: " + attrValue, e);
        }
    }

    protected String encodeUrl(final String url, final String enc) {
        if (StringUtil.isBlank(url) || StringUtil.isBlank(enc)) {
            return url;
        }

        final StringBuilder buf = new StringBuilder(url.length() + 100);
        for (final char c : url.toCharArray()) {

        if (xpath == null) {
            xpath = fessConfig.getCrawlerDocumentHtmlCanonicalXpath();
        }
        if (StringUtil.isBlank(xpath)) {
            return null;
        }
        final String canonicalUrl = getSingleNodeValue(document, xpath, node -> node);
        if (StringUtil.isBlank(canonicalUrl)) {
            return null;
        }
        return normalizeCanonicalUrl(responseData.getUrl(), canonicalUrl);
    }

            throw new PluginException("Failed to delete the artifact " + fileName, e);
        }
    }

    public Artifact getArtifact(final String name, final String version) {
        if (StringUtil.isBlank(name) || StringUtil.isBlank(version)) {
            return null;
        }
        for (final Artifact artifact : getAvailableArtifacts(ArtifactType.getType(name))) {

        if (context == null) {
            return new File[0];
        }
        final String libPath = context.getRealPath("/WEB-INF/lib");
        if (StringUtil.isBlank(libPath)) {
            return new File[0];
        }
        final File libDir = new File(libPath);
        if (!libDir.exists()) {
            return new File[0];
        }

        // TODO use cache
    }

    @Override
    public boolean visited(final OpenSearchUrlQueue urlQueue) {
        final String url = urlQueue.getUrl();
        if (StringUtil.isBlank(url)) {
            if (logger.isDebugEnabled()) {
                logger.debug("URL is a blank: {}", url);
            }
            return false;
        }