you can't lock an Entity Bean. It represents a row in the database. You'd
best not use entity beans, because what you want isn't a DB, use a message
queue instead. (http://java.sun.com/jms)
-----Original Message-----
From: Heiko Seebach [mailto:[EMAIL PROTECTED]]
Sent: Friday, June 23, 2000 5:50 AM
To: [EMAIL PROTECTED]
Subject: AW: CMP or BMP for dependent objects
Hello!
> In CMP ejbLoad() is called just after the container loads the
> data, and
> ejbStore is called just before the container will save the data.
> IMHO it is possible to do some JDBC-update here, but I am not
> sure if this
> is good practice.
Sounds good, but to be really sure: My scenario (not implemented yet, but in
my head) is, that I've several clients who work against a growing queue.
This queue is data on table, let's call it "QUEUE". The nature of a queue
is, that only one client will get some entries, and the next client will get
(by using the same finder-method) other entries in this queue.
So I would have QueueCMPEntityBean with
ejbLoad()
Statement statement=getConnection().prepareStatement("SELECT FOR
UPDATE id
FROM QUEUE WHERE id=?")
statement.setInteger(1,id);
statement.execute(); //set the lock on this entity
}
ejbStore() {
// how to release the lock here?
}
This will cause the entry to be locked, so that when another client calls
the same finder (even in worst-case only 1 cpu cycle later) will NOT get the
QueueCMPEntityBean that was returned right now, but another one (the next
one).
A call to such a finder could be:
findByIdRange(1000,1300); this returns NOT 300 entities, but only 200, since
another client could have called findByIdRange(900,1100); before
Question: Does this scenario work? How to implement ejbStore() ?
thank you very much,
Heiko
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