That sucks. I hope that the expert group can change this so that
simple pessimist locking can work portable in the future.
-dain
On Feb 21, 2008, at 1:53 PM, Evan Ireland wrote:
Dain,
Sounds like you are wanting a pessimistic lock. The semantics
of WRITE_LOCK are defined in optimistic terms in the spec.
The JPA 2.0 expert group is looking into this. In the mean time,
only non-portable apps can get this behaviour.
-----Original Message-----
From: Dain Sundstrom [mailto:[EMAIL PROTECTED]
Sent: Friday, 22 February 2008 9:50 a.m.
To: [email protected]
Subject: EntityManager.lock not working
I have a test case with two threads executing the following code:
public void run() {
try {
beginTx();
Employee david =
entityManager.getReference(Employee.class, pk);
entityManager.lock(david, LockModeType.WRITE);
entityManager.flush();
Assert.assertTrue(entityManager.contains(david));
Assert.assertEquals(david.getId(), pk);
Assert.assertEquals(david.getFirstName(), "David");
Assert.assertEquals(david.getLastName(), "Blevins");
Assert.assertEquals(1000000.0, david.getSalary());
log("READ");
// wait for other threads to read
try {
startBarrier.await(2, TimeUnit.SECONDS);
} catch (Exception e) {
}
log("WRITE");
david.setSalary(2000000);
} catch (Throwable throwable) {
this.throwable = throwable;
} finally {
try {
commitTx();
} catch (Throwable throwable) {
if (this.throwable == null) this.throwable =
throwable;
}
}
}
The first thread successfully reads the row and waits. The
second throws an exception at the entityManager.flush()
command after the write lock. I would assume that when I say
"give me a write lock"
OpenJPA would "give me a write lock". Is there anyway to get
write lock in my application for single rows without having
to switch everything to SERIALIZABLE?
-dain
