Hi Craig,
+1 to adopt the proposal.
Regards Michael
Javadogs,
I'd like to tally the vote on this issue by close of business Thursday
8-Dec-2005.
This issue was renamed to highlight the interface change.
Please vote to adopt this proposal or offer a reason to reject it. It's
the most significant change for a few months, as it modifies the core
method of persistence.
Rationale: There are so few differences between makePersistent and
attachCopy, it's confusing. The only significant differences between the
APIs is in the treatment of transient instances. MakePersistent makes
transient instances transition to persistent-new; attachCopy copies
transient instances.
The proposal is to remove attachCopy, change the signature of
makePersistent and makePersistentAll to return the instance(s).
The semantics of makePersistent change slightly from the specification.
Currently, detached instances in the object graph cause an exception to
be thrown. With this change, detached instances are located in the
persistent cache and any dirty fields are applied to the persistent
instance.
With this change, there is no standard way to attach the same object
graph to multiple persistence managers. If this becomes an issue, we can
consider adding a method to JDOHelper that copies a complete object
graph so the copies can be attached to multiple persistence managers.
But practical experience has not shown this to be an issue.
<proposed 12.6.7>
Object makePersistent (Object pc);
Object [] makePersistentAll (Object[] pcs);
Collection makePersistentAll (Collection pcs);
A12.5.7-6A [These methods make transient instances persistent and apply
detached instance changes to the cache. They must be called in the
context of an active transaction, or a JDOUserException is thrown.]
A12.5.7-6B [For a transient instance, they will assign an object
identity to the instance and transition it to persistent-new.] Any
transient instances reachable from this instance via persistent fields
of this instance will become provisionally persistent, transitively.
That is, they behave as persistent-new instances (return true to
isPersistent, isNew, and isDirty). But A12.5.7-6C [at commit time, the
reachability algorithm is run again, and instances made provisionally
persistent that are not currently reachable from persistent instances
will revert to transient.]
For a detached instance, they locate or create a persistent instance
with the same JDO identity as the detached instance, and merge the
persistent state of the detached instance to the persistent instance.
Only the state of persistent fields is merged. If non-persistent state
needs to be copied, the application should use the jdoPostAttach
callback or the postAttach lifecycle event listener. Any references to
the detached instances from instances in the closure of the parameter
instances are modified to refer to the corresponding persistent instance
instead of to the detached instance.
During application of changes of the detached state, if the JDO
implementation can determine that there were no changes made during
detachment, then the implementation is not required to mark the
corresponding instance dirty. A12.6.8-28 [If it cannot determine if
changes were made, then it must mark the instance dirty.]
No consistency checking is done during makePersistent. If consistency
checking is required by the application, then flush or checkConsistency
should be called after attaching the instances.
A12.5.7-7 [These methods have no effect on parameter persistent
instances already managed by this PersistenceManager.] A12.5.7-8 [They
will throw a JDOUserException if the parameter instance is managed by a
different PersistenceManager.]
A12.6.7-1 [If an instance is of a class whose identity type
(application, datastore, or none) is not supported by the JDO
implementation, then a JDOUserException will be thrown for that instance.]
The return value for instances in the transient or persistent states is
the same as the parameter value. The return value for detached instances
is the persistent instance corresponding to the detached instance.
The return values for makePersistentAll methods correspond by position
to the parameter instances.
</spec 12.6.7>
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!
--
Michael Bouschen [EMAIL PROTECTED] Engineering GmbH
mailto:[EMAIL PROTECTED] http://www.tech.spree.de/
Tel.:++49/30/235 520-33 Buelowstr. 66
Fax.:++49/30/2175 2012 D-10783 Berlin
