redis setIfAbsent和setnx的区别与使用说明

redis> SETNX testkey "test"
(integer) 1
redis> SETNX testkey "test"
(integer) 0
redis> GET testkey
"test"

redis> SETNX testkey "test"
(integer) 1
redis> SETNX testkey "test"
(integer) 0
redis> GET testkey
"test"

public static boolean setIfAbsent(final String key, final Serializable value, final long exptime) {
    Boolean b = (Boolean) redisTemplate.execute(new RedisCallback<Boolean>() {
        @Override
        public Boolean doInRedis(RedisConnection connection) throws DataAccessException {
            RedisSerializer valueSerializer = redisTemplate.getValueSerializer();
            RedisSerializer keySerializer = redisTemplate.getKeySerializer();
            Object obj = connection.execute("set", keySerializer.serialize(key), 
                                valueSerializer.serialize(value),
                                SafeEncoder.encode("NX"), 
                                SafeEncoder.encode("EX"), 
                                Protocol.toByteArray(exptime));
            return obj != null;
        }
    });
    return b;
}