redis-lua脚本

        redis支持lua脚本，lua脚本的详细语法和简绍不在这篇文章的总结范围。这里只说一下redis和lua的结合。

        原子性

        redis执行lua脚本是原子性的，因此可以作为事务的解决方案。

        脚本缓存

        为了加快速度，redis在load脚本的时候会生成一个sha加密的token，使用evalsha命令可以传入token执行缓存中的脚本。

        evalsha命令

        参数分别为sha token，键的数量，键名和参数。在jedis中则有多个重载的方法

        对应到lua中，参数则是table类型的变量，键名可以通过KEY[n]（n从1开始）取值。参数则通过ARGV[n]（n从1开始）取值

        清除缓存

        调用script flush命令

        示例

        

/** *  * 执行lua脚本 *  * @param scriptName * @param script * @param keyCount * @param params * @return */public static Object evalScript(String scriptName,String script,int keyCount,String ... params) {logger.info("JedisUtil.evalScript.start,scriptName="+scriptName+",\n script=["+script+"]");Jedis jedis = new Jedis(HOST, PORT);jedis.auth(PASSWORD);String sha = jedis.get("script-sha-"+scriptName);logger.info("JedisUtil.evalScript.start,scriptName="+scriptName+",sha="+sha);if(sha==null || "".equals(sha) || !jedis.scriptExists(sha)) {sha = jedis.scriptLoad(script);jedis.set("script-sha-"+scriptName, sha);logger.info("JedisUtil.evalScript.start,new sha="+sha);}logger.info("JedisUtil.evalScript.start,scriptName="+scriptName+",script="+script);Object retValue = jedis.evalsha(sha, keyCount, params);logger.info("JedisUtil.evalScript.end,retValue="+retValue);return retValue;}

/** *  * 清除lua脚本缓存 *  * @return */public static boolean flushScript() {logger.info("JedisUtil.flushScript.start");Jedis jedis = new Jedis(HOST, PORT);jedis.auth(PASSWORD);String retValue = jedis.scriptFlush();logger.info("JedisUtil.flushScript.end,retValue="+retValue);if("OK".equals(retValue.toUpperCase())) {return true;} else {return false;}}

private final static String GET_JSON_SCRIPT = "redis.log(redis.LOG_NOTICE, \"get json start\") " +  "if redis.call(\"EXISTS\", KEYS[1]) == 1 then " +  "    redis.log(redis.LOG_NOTICE, \"get json,key:\" .. KEYS[1]) " +  "   local payload = redis.call(\"GET\", KEYS[1]) " +  "   redis.log(redis.LOG_NOTICE, \"get json,payload:\" .. payload) " +  "    local value = cjson.decode(payload)[ARGV[1]] " +  "   redis.log(redis.LOG_NOTICE, \"get json,value:\" .. value) " +  "   return value " +  "else " +  "    redis.log(redis.LOG_NOTICE, \"get json,not found key,key:\" .. KEYS[1]) " +  "   return nil " +  "end";private final static String GET_JSON_SCRIPT_NAME = "GET_JSON_SCRIPT";

/** *  * 获得json格式数据的值 *  * @param key * @param jsonKey * @return */public static Object getJson(String key, String jsonKey) {logger.info("JedisUtil.getJson.start,key="+key+",jsonKey="+jsonKey);Jedis jedis = new Jedis(HOST, PORT);jedis.auth(PASSWORD);Object retValue = evalScript(GET_JSON_SCRIPT_NAME,GET_JSON_SCRIPT,1,key,jsonKey);logger.info("JedisUtil.getJson.end,retValue="+retValue);return retValue;}

public static void main(String[] args) {try { JedisUtil.set("test", "{\"a\":\"s\",\"b\":\"t\"}");//JedisUtil.flushScript();Object retValue = JedisUtil.getJson("test", "b");System.out.println("----------------"+retValue+"----------------"); } catch (Exception e) {e.printStackTrace();}}