Boulatian, Misak wrote:
Hi,
We have a big problem using EJB 2.0 with jboss. We use Updatable Value
Object Pattern (currently, Transfer Object Pattern). This means we have
individual get and set methods in entity bean's remote interface and
also have setData methods to make changes in entity bean's attributes in
one remote method call. As you know, this may introduce Stale Value
Objects. Before considering using CMP 2.0 we were using CMP 1.1. We had
version control attribute that was updated in every set method call of
bean class. getData method copied the current value of version control
in the Value Object and sent it to the client. When updated Value Object
was sent back through setData, the implementation of setData within bean
class compared version attribute value with the copy of the bean class
and threw appropriate exception if they were not the same.
Using CMP 2.0 we can no longer update version control attribute since
all set methods are abstract. We thought we can increment version
control within ejbStore but jboss can call it without even any entity
bean attribute change (very inpredictable). So, we thought we can use
optimistic tag and specify version control attribute within
jbosscmp-jdbc, but this doesn' t seem to be the case either.
I have the following questions:
1) When bean developer specifies version control attribute, does jboss
update its value?
Yes.
2) If it does, then does jboss compare its value in Value Object Pattern
scenario and throw any exception? If it does then what is the exception
type?
On synchronization, the version field is added to the WHERE clause of
the UPDATE statement. Like UPDATE WHERE PK = ? AND VERSION = ?
If failed, TransactionRolledBack exception is thrown.
3) If jboss doesn't compare, is there a way that bean developer can
compare to let client know of differences?
The version field can be implicit and explicit. Explicit means it is a
real cmp-field that has CMP getter and setter and is declared in
ejb-jar.xml. JBoss will update this field as above. And you still can
use its getter to check the value.
4) If none of these applies then I would like to hear how this
optimistic tag with version-control works so we can try to use jboss
with CMP 2.0
Seems to be answered.
5) Is there any other way to do version control check in jboss using CMP
2.0 to avoid stale objects problem (weblogic has similar version control
and automatically checks and throws exception if versions do not match).
How does it work in weblogic?
It seems like with CMP 2.0 it is the container's responsibility to
provide for this type of solution.
Yes. But this is not defined in the spec.
If jboss doesn't have this then how
can we use jboss with CMP 2.0 in production.
I think, you can do it.
Or, because of this, we
have to use CMP 1.1 only if we still want to stay on jboss.
I really appreciate the response.
Thanks,
Misak
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