private void processRequest(Request request) {
        Page page;
        if (null != request.getDownloader()){
            page = request.getDownloader().download(request,this);
        }else {
            page = downloader.download(request, this);
        }
        if (page.isDownloadSuccess()){
            onDownloadSuccess(request, page);
        } else {
            onDownloaderFail(request);
        }
    }
Process specific urls without url discovering.

@param urls urls to process
webmagic-core/src/main/java/us/codecraft/webmagic/Spider.java