[lock] redis lock handles concurrency atomicity

【 lock 】Redis lock Concurrent processing Atomicity

If it is empty, then set value , And back to 1
If there is ( Not empty ) No operation , And back to 0

Obviously , Than get and set It is better to . Because judge first get, Again set Usage of , It's possible to repeat set value .

setIfAbsent and setnx
setIfAbsent yes java The method in
setnx yes redis Methods in the command

explain ： When key non-existent , take key The value of the set value, And set expiration time , return true; If a given key Already exist , Then do nothing , And back to false. This method is atomic

@Autowired
private RedisTemplate redisTemplate;
 
/**
 *  Lock 
 * @param key key
 * @param value value
 * @param timeout  Expiration time in seconds 
 * @param false Indicates a lock  / true Express key non-existent   unlocked 
 */
public boolean getLock(String key, String value, long timeout) {
	 try {
		 // Atomic operation 
		 boolean flag = redisTemplate.opsForValue().setIfAbsent(key, value, timeout, TimeUnit.SECONDS);
		 // If there is false It means repetition 
		 return flag;
	 } catch (Exception e) {
		 logger.error("redis Abnormal locking ", e);
         // An exception occurred to delete the lock 
		 redisTemplate.delete(key);		
		 return true;
	 }
}

redis command

redis> SETNX mykey "Hello"
(integer) 1
redis> SETNX mykey "World"
(integer) 0
redis> GET mykey
"Hello"