public <T> List<T> getAll(Collection<String> urls) {
        destroyWhenExit = false;
        spawnUrl = false;
        if (startRequests!=null){
            startRequests.clear();
        }
        for (Request request : UrlUtils.convertToRequests(urls)) {
            addRequest(request);
        }
        CollectorPipeline collectorPipeline = getCollectorPipeline();
        pipelines.add(collectorPipeline);
        run();
        spawnUrl = true;
        destroyWhenExit = true;
        return collectorPipeline.getCollected();
    }
Download urls synchronizing.

@param urls urls
@param <T> type of process result
@return list downloaded
webmagic-core/src/main/java/us/codecraft/webmagic/Spider.java