@Override
    protected void pushWhenNoDuplicate(Request request, Task task) {
        if (!inited.get()) {
            init(task);
        }
        queue.add(request);
        fileUrlWriter.println(serializeRequest(request));
    }
Store urls and cursor in files so that a Spider can resume the status when shutdown.<br>

@author code4crafter@gmail.com <br>
@since 0.2.0
webmagic-extension/src/main/java/us/codecraft/webmagic/scheduler/FileCacheQueueScheduler.java