I tried :
PersistenceManager pm = PMF.get().getPersistenceManager();
try
{
DatastoreService datastore =
DatastoreServiceFactory.getDatastoreService();
Query query = new Query("__Stat_Kind__");
query.addFilter("kind_name", FilterOperator.EQUAL,
Gestionnaire.class.getName());
Entity stat = datastore.prepare(query).asSingleEntity();
Long count = (Long) stat.getProperty("count");
if(count.equals(0))
{
Gestionnaire admin = new Gestionnaire
("admin","chuck");
pm.makePersistent(admin);
return "base initialisée";
}
else return "base déjà initialisée";
}
but the line : Long count = (Long) stat.getProperty("count"); throws
a nullPointerException
On 15 mar, 03:44, John Patterson <[email protected]> wrote:
> Use the __Stat_total__ pseudo kind
>
> http://code.google.com/appengine/docs/java/datastore/stats.html
>
> On 15 Mar 2010, at 09:36, Robert Lancer wrote:
>
> > A query has to specify an entity kind as its minimum parameter, and
> > then doing a count and seeing if its equal to zero for a known entity
> > kind would be the best way.
>
> > On Mar 13, 1:44 pm, vchalmel <[email protected]> wrote:
> >> hi !
>
> >> I want to set up an initialization script, and i must, in a first
> >> part, check if the appengine datastore is empty.
> >> I tried to send a query, with :
>
> >> query.setUnique(true);
> >> if(query.execute()==null)
>
> >> But it throws a null pointer exception.
>
> >> How to check that my datastore is empty ?
>
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