Multi Threading problem (Complex issue)

avihaimar · **Joined:** Thu Nov 02, 2006 2:23 pm **Posts:** 33

Hey,

Lets say i have a Buyer obj , each Buyer has reference to BooksCollection obj .The primary key of BooksCollection is the hash value of the names of the books that it contains.

In the BuyerDAO i check (by session.get ) if the BooksCollection already in the seesion.

In case it is i get it from the session and set it to the Buyer

Than call to session.saveOrUpdate(Buyer)

Scenario:
Multi thread application.
Two Buyer with the same BooksCollection from differents threads come in the same time.

Code:

Exception - java.sql.SQLException: Duplicate entry '1075191317' for key 1

I close the session and try to save (The same logic like above) the Buyer again , but faild with :

Code:

org.hibernate.StaleStateException: Unexpected row count: 0 expected: 1

Please, Please ,Please,
I am trying to sove it for a long time.

Thank you

scarface · **Joined:** Sun Jun 04, 2006 1:58 am **Posts:** 136

session impls are not thread safe

It is not intended that implementors be threadsafe. Instead each thread/transaction
* should obtain its own instance from a <tt>SessionFactory

avihaimar · **Joined:** Thu Nov 02, 2006 2:23 pm **Posts:** 33

I think that the problem in the first try is that the same BookCollection arrive at the same time (this is a webservice , so different threds, different session), so when they check if BookCollection is already exists they get false and they both trying to save it at the same time, so only one success (duplicate). i dont know how to solve it.

In the second try the BookCollection is already exists, it get it from the session and do saveOrUpadte to buyer , but failed because StaleStateException , i have no idea why, and how to debug it.

Thank you