this.logger = requireNonNull(logger);
    }

    public void debug(CharSequence content) {
        if (isDebugEnabled()) {
            logger.debug(toString(content));
        }
    }

    @Override
    public void debug(CharSequence content, Throwable error) {
        if (isDebugEnabled()) {
            logger.debug(toString(content), error);
        }
    }

    @Override

    public void add(final ThumbnailGenerator generator) {
        if (generator.isAvailable()) {
            if (logger.isDebugEnabled()) {
                logger.debug("{} is available.", generator.getName());
            }
            generatorList.add(generator);
        } else if (logger.isDebugEnabled()) {
            logger.debug("{} is not available.", generator.getName());
        }
    }

                if (logger.isDebugEnabled()) {
                    logger.debug("principal: {}", principal);
                }
            } catch (final Exception e) {
                final String msg = "Failed to process Authorization Header: " + request.getHeader(Constants.AUTHZ_HEADER);
                if (logger.isDebugEnabled()) {
                    logger.debug(msg);
                }

            }
        } catch (final ContainerNotAvailableException e) {
            if (logger.isDebugEnabled()) {
                logger.debug("container was destroyed.");
            }
            return;
        } catch (final Exception e) {
            if (!ComponentUtil.available()) {
                if (logger.isDebugEnabled()) {
                    logger.debug("container was destroyed.");
                }

                    .get(stream -> stream.map(String::trim).filter(StringUtil::isNotBlank).collect(Collectors.toUnmodifiableSet()));
        }
        if (logger.isDebugEnabled()) {
            logger.debug("availableSearcherNameSet={}", availableSearcherNameSet);
        }
    }

    @Override
    @PreDestroy
    public void close() throws Exception {

                if (extractor == null) {
                    if (logger.isDebugEnabled()) {
                        logger.debug("use a defautl extractor as {} by {}", extractorName, mimeType);
                    }
                    extractor = crawlerContainer.getComponent(extractorName);
                } else if (logger.isDebugEnabled()) {

            }, OptionalThing.empty());
            response.flushBuffer();
            if (logger.isDebugEnabled()) {
                logger.debug("Loaded {} docs", count);
            }
        } catch (final InvalidQueryException | ResultOffsetExceededException e) {
            if (logger.isDebugEnabled()) {
                logger.debug("Failed to process a scroll request.", e);
            }

    }

    public void delete(final String badWord) {
        if (logger.isDebugEnabled()) {
            logger.debug("Delete badword. {} badword: {}", arraySettings.arraySettingsIndexName, badWord);
        }
        arraySettings.delete(BAD_WORD_SETTINGD_KEY, badWord);
    }

    public void deleteAll() {
        if (logger.isDebugEnabled()) {
            logger.debug("Add all badword. {}", arraySettings.arraySettingsIndexName);

                    forceStop();
                    break;
                }
            }

            if (logger.isDebugEnabled()) {
                logger.debug("Finished indexUpdater.");
            }
        } catch (final ContainerNotAvailableException e) {
            if (logger.isDebugEnabled()) {
                logger.error("IndexUpdater is terminated.", e);
            } else if (logger.isInfoEnabled()) {

    }

    @Override
    public boolean generate(final String thumbnailId, final File outputFile) {
        if (logger.isDebugEnabled()) {
            logger.debug("Generate Thumbnail: {}", thumbnailId);
        }

        if (outputFile.exists()) {
            if (logger.isDebugEnabled()) {
                logger.debug("The thumbnail file exists: {}", outputFile.getAbsolutePath());
            }
            return true;