return builder;
        } catch (final IOException e) {
            throw new OpenSearchAccessException("Failed to convert " + target + " to JSON.", e);
        }
    }

    protected RefreshResponse refresh() {
        try {
            return getClient().get(c -> c.admin().indices().prepareRefresh(index).execute());
        } catch (final Exception e) {

    }

    public void start() {
        try {
            server.start();
        } catch (final Exception e) {
            throw new CrawlerSystemException(e);
        }
    }

    public void stop() {
        try {
            server.stop();
            server.join();
        } catch (final Exception e) {
            throw new CrawlerSystemException(e);
        } finally {

    @PreDestroy
    public void destroy() {
        sessionCache.entrySet().stream().map(e -> e.getValue().waitingQueue).forEach(q -> q.forEach(urlQueue -> {
            try {
                insert(urlQueue);
            } catch (final Exception e) {
                logger.warn("Failed to restore " + urlQueue, e);
            }
        }));
    }

    public void clearCache() {
        sessionCache.clear();
    }

    @Override

        try {
            return includeFilterCache.get(sessionId);
        } catch (final ExecutionException e) {
            throw new CrawlerSystemException(e);
        }
    }

    @Override
    public List<Pattern> getExcludeUrlPatternList(final String sessionId) {
        try {
            return excludeFilterCache.get(sessionId);
        } catch (final ExecutionException e) {
            throw new CrawlerSystemException(e);

            try {
                return func.apply(this).actionGet(connTimeout, TimeUnit.MILLISECONDS);
            } catch (final IndexNotFoundException | VersionConflictEngineException e) {
                logger.debug("{} occurs.", e.getClass().getName(), e);
                throw e;
            } catch (final Exception e) {
                if (retryCount > maxRetryCount) {
                    throw e;
                }

        setEncoding((String) src.get(ENCODING));
        final String dataStr = (String) src.get(DATA);
        if (dataStr != null) {
            try {
                setData(Base64Util.decode(dataStr));
            } catch (final Exception e) {
                throw new OpenSearchAccessException("data: " + dataStr, e);
            }
        }
    }

    @Override

                    setId(target, searchHit.getId());
                    targetList.add(target);
                }
            } catch (final Exception e) {
                throw new OpenSearchAccessException("response: " + response, e);
            }
        }
        return targetList;
    }

    @SuppressWarnings("unchecked")