This isn't available in the low level API. Transactions are already using the implementation you've described via optimistic locking.
There's an article written by Max Ross about using the @Version annotation to achieve the same thing. Check it out: http://gae-java-persistence.blogspot.com/2009/10/optimistic-locking-with-version.html On Thu, May 13, 2010 at 11:54 PM, brendan <[email protected]> wrote: > Slide 54 of Under the Covers of the Google App Engine Datastore by > Ryan Barrett states that the "last committed timestamp co-located with > root entity". Is it possible to access this last committed timestamp > using the low level datastore API? > > I'd like to be able to access it to create an enhancement to objectify > that provides optimistic locking. > > My idea is: > - On get(), populate a field in the entity just read with the > timestamp. Probably the field would have an @Lock annotation. > - Send entity to gwt client over rpc. > - Receive entity back from gwt client over rpc. > - On put(), before update check the timestamp and fail if their is a > difference. > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine for Java" group. > To post to this group, send email to > [email protected]. > To unsubscribe from this group, send email to > [email protected]<google-appengine-java%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/google-appengine-java?hl=en. > > -- Ikai Lan Developer Relations, Google App Engine Twitter: http://twitter.com/ikai Delicious: http://delicious.com/ikailan ---------------- Google App Engine links: Blog: http://googleappengine.blogspot.com Twitter: http://twitter.com/app_engine Reddit: http://www.reddit.com/r/appengine -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.
