private Request getExtrasInItem(Jedis jedis, String url, Task task) {
        String key      = getItemKey(task);
        String field    = DigestUtils.sha1Hex(url);
        byte[] bytes    = jedis.hget(key.getBytes(), field.getBytes());
        if (bytes != null) {
            return JSON.parseObject(new String(bytes), Request.class);
        }
        return new Request(url);
    }
the redis scheduler with priority
@author sai
Created by sai on 16-5-27.
webmagic-extension/src/main/java/us/codecraft/webmagic/scheduler/RedisPriorityScheduler.java