redis issue business code

[Junobee25]

1. 
@PostMapping("/redis-stock/purchase")
    public Response<Void> purchase(@RequestBody StockAdapterDto request) {
        redisStockService.purchase(request);
        return Response.success();
    }
2.
public void purchase(StockAdapterDto stockAdapterDto) {
        redisStockRepository.decrementStock(stockAdapterDto.productId(), stockAdapterDto.quantity());
    }

3.
public void decrementStock(Long productId, Integer quantity) {
        String key = getKey(productId);
        RedisStock redisStock = redisTemplate.opsForValue().get(key);

        redisStock.verifyRemainAvailability(quantity);
        redisStock.setRemain(redisStock.getRemain() - quantity);
        redisTemplate.opsForValue().set(key, redisStock);
    }

Redis inventory classes are:

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
public class RedisStock implements Serializable {

    private Long productId;
    private Integer remain;

    public void verifyRemainAvailability(final Integer quantity) {
        if ((remain - quantity) < 0) {
            throw new IllegalArgumentException();
        }
        remain -= quantity;
    }
}