}).toList();
        if (fessConfig.isThumbnailCrawlerEnabled()) {
            final ThumbnailManager thumbnailManager = ComponentUtil.getThumbnailManager();
            final String thumbnailField = fessConfig.getIndexFieldThumbnail();
            docList.stream().forEach(doc -> {
                if (!thumbnailManager.offer(doc)) {
                    if (logger.isDebugEnabled()) {

            throw responseManager.new404("Thumbnail for " + form.docId + " is not found.");
        }

        final File thumbnailFile = thumbnailManager.getThumbnailFile(doc);
        if (thumbnailFile == null) {
            if (fessConfig.isThumbnailEnabled()) {
                thumbnailManager.offer(doc);
            }
            // 404
            throw responseManager.new404("Thumbnail for " + form.docId + " is under generating.");

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE components PUBLIC "-//DBFLUTE//DTD LastaDi 1.0//EN"
	"http://dbflute.org/meta/lastadi10.dtd">
<components>
	<component name="thumbnailManager" class="org.codelibs.fess.thumbnail.ThumbnailManager">
	</component>
	<component name="htmlThumbnailGenerator" class="org.codelibs.fess.thumbnail.impl.HtmlTagBasedGenerator">
		<property name="name">"htmlThumbnailGenerator"</property>
		<postConstruct name="addCondition">