Java中的线程同步问题

Question

I am working on Soap WebServices application using hibernate. In that I am generating orderNumbers for each order. To do so I have following table with two fields

ORDER_SERIES LAST_ORDER_COUNT

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ORD 250

To generate ORDER_NO first I get the record from above table and increament LAST_ORDER_COUNT by 1 and append with ORDER_SERIES

so my ORDER_NO would be ORD251

after that I am updating above table with new increamented LAST_ORDER_COUNT

ORDER_SERIES LAST_ORDER_COUNT

---

ORD 251

I have written one Method to do this operation means get record from table, increament LAST_ORDER_COUNT append both and return order no and update LAST_ORDER_COUNT. I made this method as synchronized.

but in production environment I am getting duplicate ORDER_NOs

my soap webservices are getting Called through android apk.

any idea why ORDER_NO are getting duplicate

Answer 1

Id should be auto increment in the database and it should be a primary/Unique key as well. if you will not do so then in future, you would face such type of issue when you will have more request simultaneously.