Re: [jira] Commented: (OPENJPA-396) Cloning Calendar proxies doesn't detach from StateManager

[Craig L Russell]

Hi Pinaki,

On Oct 8, 2007, at 11:35 AM, Pinaki Poddar wrote:

I am proposing to modify
the generated proxy code to override the clone() method.  This
clone() method will do the necessary copying of data from the
original object, but then also null out the sm (StateManager)
and zero out the field attributes.  This action detaches the
cloned object from the StateManager (and associated EntityManager).

Who will invoke this Proxy.clone()? and when?

This is mostly from memory. If I get it too wrong, then you can take all of my comments on this as a whiff of fresh air.

Are we now having
A) the original user object x

No, if you fetch an instance from the database with a field of type Calendar, all you get is a proxy.

B) the proxy of x

Yup, this is the value of the field.

C) clone of proxy of x

If you clone the proxy, you get a clone. Which should not have anything to do with the original proxy.

D) copy of proxy of x, as generated by Proxy.copy()

I don't know of any use for this.

will the change in SCO be tracked in remote client?

If the clone with no owning statemanager is the 'detached' SCO, then how

The bug refers to a strange usage of clone by the IBM VM. ;-)



Craig

The clone with no owning statemanager should never be the value of any field, whether attached or detached. If a clone is set as the value of a field, then the enhanced putfield method should assign ownership of that clone to the statemanager of the instance whose field is being set. And then the clone is no longer a clone but a bona fide proxy that has an owner.

Pinaki Poddar
972.834.2865

-----Original Message-----
From: Kevin Sutter (JIRA) [mailto:[EMAIL PROTECTED]
Sent: Monday, October 08, 2007 12:54 PM
To: dev@openjpa.apache.org
Subject: [jira] Commented: (OPENJPA-396) Cloning Calendar
proxies doesn't detach from StateManager


   [
https://issues.apache.org/jira/browse/OPENJPA-396?page=com.atla
ssian.jira.plugin.system.issuetabpanels:comment-tabpanel#action
_12533169 ]

Kevin Sutter commented on OPENJPA-396:
--------------------------------------

[ Show > ]
Craig Russell - 08/Oct/07 10:25 AM Hi Kevin, One question. In
the generated clone method, after calling super.clone(), why
do you not simply invoke stateManager = null; pcState = 0;
instead of calling the setOwner(null, 0) method? Seems like
there is additional code in setOwner that you want to avoid
because there is not yet any relationship between the owner
and the sco. The effect of calling this method from the clone
might be to disassociate the original sco.

Craig,
The original reason is that I couldn't figure out the proper
serp invocations to just set those two fields.  :-)  Then, I
found the setOwner method on the Proxy (also generated code)
that did just what I was looking for.  So, it was more


As far as I can tell, the setOwner has no other side effects.
I am calling setOwner on the Proxy, not the StateManager.  The
code is generated in the ProxyManagerImpl class
(addProxyMethods method).  And, the javadoc for this method is
as follows:

   /**

    * proxy and the name of the field it is assigned to. Set
to null to
    * indicate that the proxy is no longer managed.
    */
   public void setOwner(OpenJPAStateManager sm, int field);

Kevin

straight-forward to just call this method than to repeat the same code. * Reset the state of the proxy, and set the owning instance of the

Cloning Calendar proxies doesn't detach from StateManager
---------------------------------------------------------

                Key: OPENJPA-396
                URL:

https://issues.apache.org/jira/browse/OPENJPA-396

            Project: OpenJPA
         Issue Type: Bug
         Components: kernel
   Affects Versions: 1.0.0, 1.0.1, 1.1.0
           Reporter: Kevin Sutter
           Assignee: Kevin Sutter
            Fix For: 1.0.1, 1.1.0

        Attachments: OPENJPA-396.patch


This problem was first discussed on our dev mailing list:
http://www.nabble.com/Cloning-Calendar-proxies-tf4571181.html
Per the discussion on that thread, I am proposing to modify

the generated proxy code to override the clone() method.  This
clone() method will do the necessary copying of data from the
original object, but then also null out the sm (StateManager)
and zero out the field attributes.  This action detaches the
cloned object from the StateManager (and associated EntityManager).

Instead of limiting this action to the Calendar proxy, I am

adding the clone() method implementation to all of our proxy
objects that we generate.  Granted, some of the object types
do not directly support the clone() method, but that will be
detected when or if anybody attempts to use the clone() method
on these types (compiler generated error message).

I'll be posting a patch shortly and I plan to commit the

changes later today (unless there is opposition).

Thanks,
Kevin

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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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