1) Open the connection --> create a broker
2) Begin a transaction -> broker.beginTransaction or, if JTA, userTransaction.begin()
3) Call some method, for example create(object)
4) Commit transaction
5) if any exception, rollback transaction
6) finally, close resources --> broker.close();
In the case of method 'create', I set transaction isolation level in the following way:
Connection con = broker.serviceConnectionManager().getConnection(); con.setTransactionIsolation(Connection.TRANSACTION_REPEATABLE_READ);
Then I create the object, so the sequencer is called within this isolation level. And at the end, the BO will finally close resources.
From: Armin Waibel <[EMAIL PROTECTED]> Reply-To: "OJB Users List" <[EMAIL PROTECTED]> To: OJB Users List <[EMAIL PROTECTED]> Subject: Re: Sequencers in clustered environment Date: Tue, 11 May 2004 14:21:54 +0200
Hi Enrique,
Enrique Medina wrote:
Hi,
I've read the tutorial about how to work in a clustered environment, specially the part that has to be with sequencers.
Using a Lock Column is a good solution, but as the nextVal cannot be rolled back, we would miss many possible codes.
So I have implemented a sequencer that extends AbstractSequenceManager and implements getUniqueLong() executing a SELECT that returns the MAX(ID) from the table. To be sure that it works in a clustered environment, I assure that the broker that is passed to the constructor of my sequencer has set transaction isolation level to REPEATABLE_READ, as EJB do.
How do you assure that the passed PB instance use REPEATABLE_READ tx-level? Do you change transaction isolation at runtime using Connection.setTransactionIsolation? When do you change it, reset old state?
regards, Armin
I would appreciate some suggestions and posible alternatives or misconceptions I may have with this solution.
Thanks in advance, Enrique Medina.
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