Javadogs,
Please comment on this proposal.
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), and
add a method to JDOHelper.
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. So a method is added to
JDOHelper that copies a complete object graph so the copies can be
attached to multiple persistence managers.
Instead of:
Object[ ] attached1 = pm.attachCopy(graph);
Object[ ] attached2 = pm.attachCopy(graph);
use:
Object[ ] copies = JDOHelper.shallowCopy(graph, false);
Object[ ] attached1 = pm.makePersistentAll(copies);
Object[ ] attached2 = pm.makePersistentAll(copies);
The signatures of shallowCopy are:
Object shallowCopy(Object original, boolean copyTransientFields);
Collection shallowCopyAll(Collection original, boolean
copyTransientFields);
Object[ ] shallowCopy(Object[ ] original, boolean copyTransientFields);
The copyTransientFields parameter specifies whether to copy the
transient fields of detached and transient instances. True requires
that the JDOHelper be given security privileges to allow reflective
copy. Non-binary-compatible implementations also require security
privileges. Binary-compatible implementations will use the support
for PersistenceCapable to copy the fields.
Support for deep copies is left to the implementation, as there is no
standard way to deep copy.
Craig
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!
