MyBatis 原生二级缓存"难以修复"的原因解析及解决方案

@Mapper
@CacheNamespace(implementation = RedisCache.class)
public interface OrderMapper {
    // ...
}

public class VersionedCache implements Cache {
    private final String id;
    private final RedisTemplate redis;
    @Override
    public void putObject(Object key, Object value) {
        // key = "order:123", value = { data: {...}, version: 20251203 }
        redis.opsForHash().put("mybatis:cache:" + id, serialize(key), wrapWithVersion(value));
    }
    @Override
    public Object getObject(Object key) {
        Object cached = redis.opsForHash().get("mybatis:cache:" + id, serialize(key));
        if (cached != null && isVersionValid(cached)) {
            return unwrap(cached);
        }
        return null;
    }
}

@Service
public class OrderService {
    public Order getOrder(Long id) {
        String cacheKey = "order:v2:" + id;
        Order order = redis.get(cacheKey, Order.class);
        if (order != null) return order;
        // 双检锁 + 空值缓存防穿透
        synchronized (getLockKey(id)) {
            order = redis.get(cacheKey, Order.class);
            if (order == null) {
                order = orderMapper.findById(id);
                if (order != null) {
                    redis.setex(cacheKey, 300, order); // 5分钟过期
                } else {
                    redis.setex("empty:" + cacheKey, 60, "1"); // 防缓存穿透
                }
            }
        }
        return order;
    }
    @Transactional
    public void updateOrder(Order order) {
        orderMapper.update(order);
        // 主动失效缓存（旁路删除）
        redis.delete("order:v2:" + order.getId());
    }
}