Do yourself a big favor and run away from JDO + GAE screaming as fast
as you can. You're much better off using one of the thin wrappers
around the AppEngine Datastore like Objectify or Twig along with the
built in Memcache service.
JDO was designed for relational data models, GAE was designed for the
opposite. They don't play well together. You *can* get them to work,
and many have, but I have yet to find anyone who enjoyed the
experience.
best,
Rick
On Jan 1, 7:07 pm, The night manager <peter.dunay.kov...@gmail.com>
wrote:
> Hi,
>
> I am new to both GAE and JDO. I would be grateful if someone could provide
> guidance on a behavior I find rather counter-intuitive. In the following
> code, I have to call pm.evictAll() to successfully/persistently change
> properties (labels) on a freshly persisted object (bookmark):
>
> PersistenceManager pm = PMF.get().getPersistenceManager();
> try {
> Bookmark bookmark = new Bookmark(url);
> bookmark = pm.makePersistent(bookmark);
> pm.evictAll();
> Key k = bookmark.getKey();
> bookmark = pm.getObjectById(Bookmark.class, k);
> bookmark.addLabels(labels);
>
> } finally {
> pm.close();
> }
>
> I'd naively expect the above code to persistently adding labels to
> bookmarkseven without calling
> pm.evictAll()and with explicitly (re-)fetching the bookmark object. I'd
> expect JDO to "notice" that the Bookmark instance has been "dirtied" and
> pm.close() to persist the changes to the cached object.
>
> I find it also counter-intuitive that pm.evict(bookmark) doesn't work --
> the entire cache needs to be cleared for new labels on bookmark to get
> persisted. (Even though pm.evict(Object) appears to expect a *
> persistent-clean* object, which, in turn, appears to assume being in a
> transaction...)
>
> Any pointers on the reasons of this behavior will be gratefully appreciated.
>
> Peter
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