It seems that adding a version field in product entity will work.
> On 10 Sep 2018, at 11:43 AM, Willem Jiang <[email protected]> wrote:
>
> Hi，
>
> I submitted a PR[1] to show how to use TCC with JPA. There are some
> missing points with my limited knowledge of JPA. So I just send out
> this email to ask help from community.
>
> In the inventory service[2], we need to update the product in stock
> number[3]. As the reserver method could be invoked in multiple
> threads at the same time and JPA doesn't provide the isolation across
> these thread[4]. We may need to add optimis lock or use version to
> keep track for the change. But I didn't manage to get workable code
> by applying the optimic lock or using the version file to prevent the
> lost updates[5].
>
> So I'm asking help from the expert of JPA for an example of this case.
>
> [1]https://github.com/apache/incubator-servicecomb-saga/pull/290
> [2]https://github.com/apache/incubator-servicecomb-saga/tree/SCB-820/saga-demo/tcc-spring-demo/inventory
> [3]https://github.com/apache/incubator-servicecomb-saga/blob/SCB-820/saga-demo/tcc-spring-demo/inventory/src/main/java/org/apache/servicecomb/saga/demo/pack/inventory/InventoryService.java#L44
> [4]https://vladmihalcea.com/a-beginners-guide-to-database-locking-and-the-lost-update-phenomena/
> [5]https://vladmihalcea.com/preventing-lost-updates-in-long-conversations/
>
>
> Willem Jiang
>
> Twitter: willemjiang
> Weibo: 姜宁willem
