26 redis-lua表达式怎么写？代码里写lua脚本有啥优缺点？

String script =
    "local stock = redis.call('GET', KEYS[1]) " +
    "if not stock then return -2 end " +
    "stock = tonumber(stock) " +
    "local deduct = tonumber(ARGV[1]) " +
    "if stock < deduct then return -1 end " +
    "redis.call('DECRBY', KEYS[1], deduct) " +
    "return stock - deduct";

Long result = redisTemplate.execute(
    new DefaultRedisScript<>(script, Long.class),
    Collections.singletonList("product:stock:1001"),
    "1"
);

if (result >= 0) {
    // 成功，下单
} else if (result == -1) {
    // 库存不足
} else {
    // 库存不存在
}