public static DownloadTask create(String url, String savePath, int downloaderCount) throws IOException, CloneNotSupportedException {
		//从记录文件中读取url，如果url为null的话
		if (CommonUtils.isStringNullOrWhiteSpace(url) &&
				!CommonUtils.isStringNullOrWhiteSpace(FileUtil.getBaseNameByPath(savePath))) {
			url = DownloadRecord.load(new File(DownloadTask.getRecordFilePath(savePath))).url;
		}
		if (CommonUtils.isStringNullOrWhiteSpace(url)) throw new MalformedURLException();

		String downloadAt = getDownloadAt(url, savePath);
		if (new File(downloadAt).exists())
			throw new FileAlreadyExistsException(downloadAt);

		return new DownloadTask(url, downloadAt, downloaderCount);
	}