Re: detachable vs non detachable classes serialization compatible

[Craig L Russell]

Hi Erik,




Thanks,

Craig

On May 7, 2007, at 5:31 PM, Erik Bengtson wrote:

These are implementation details. Can you explain what the user behavior is, and the use case?

Craig,


Serialization Code.



Default Serialization:


enhancer adds the following:

private writeObject (OutputStream os) //enhanced
{
jdoPreSerialize();
os.defaultWriteObject()
}

User Serialization (user defined writeObject and readObject methods):

private writeObject (OutputStream os)
{
jdoPreSerialize(); //enhanced
//user serialization
os.writeObject(jdoDetachedState) //enhanced
}

private readObject (OutputStream os)
{
//user serialization
jdoDetachedState = os.readObject(); //enhanced
}



Quoting Craig L Russell <[EMAIL PROTECTED]>:

There are two cases: Classes using default Serialization and classes with User In all cases the User must add serialVersionId field to the non enhanced class. The default serialization will take care of dropping the jdoDetachedState. The

Hi Erik,

It would help if you could explain what you have in mind with this
change. The decision to make the detachable serialization contract
incompatible was deliberate, and the objective is to guarantee that
attaching a detached instance behaves correctly.

If you want a detached instance simply to send it away and never
expect to see it again, your proposal might be of interest. Is that
what you had in mind?

Do you have some ideas on how to implement this feature? Seems that
if the unenhanced class is given an input stream with the detached
info in the serialized form of the instance, it's going to run into
an exception (unless you modify the unenhanced class, perhaps with a
byte-code enhancer).

Thanks,

Craig

On May 6, 2007, at 5:39 AM, Erik Bengtson wrote:

Hi,

The spec says classes that detachable and non detachable classes
are not
compatible intentionally. I would like to propose a change to this
behavior and
let the “jdoDetachedState” lose on unmarshalling.

From:
"Classes marked as Detachable are not serialization-compatible with
un-enhanced
classes. This is intentional, and requires that the enhanced
version of the
class be used wherever the instance might be instantiated."

To:
"Classes marked as Detachable are not serialization-compatible with
un-enhanced
classes. When unmarshalling a detached object with an un-enhanced
version of
the class, the detached state is dropped and no further read or
change tracking
will occur on the unmarshalled instance."

Regards,

Erik Bengtson

Craig Russell

Architect, Sun Java Enterprise System http://java.sun.com/products/ jdo

408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!

Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!

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