Google App Engine HR数据存储-Java-以编程方式删除实体

Question

I am running Google App Engine in my Eclipse (Helios) IDE. I use Java for Implementation. Testing is done locally on localhost:8888.

Unfortunately I cant solve the following problem. I store Entities in Google app Engine High Replication Datastore. Key is the location, all events are stored as kinds of location (as i understand) with no special unique primary key right now. I use:

DatastoreService dss;
Key key;
Entity event;

dss = DatastoreServiceFactory.getDatastoreService();
key = KeyFactory.createKey("location", location);  //location is String

event = new Entity("event", key);
event.setProperty("date", date);
event.setProperty("info", infostrg);
dss.put(event);

This works fine.

When I try to get all events taking place in a specific location I use the follewing code:

dss = DatastoreServiceFactory.getDatastoreService();

key = KeyFactory.createKey("location", location);
aktQuery = new Query ("event", key);

aktQuery.addSort("date", Query.SortDirection.DESCENDING);       
//List<Entity>
events = dss.prepare(aktQuery).asList(FetchOptions.Builder.withLimit(20));

for (Entity event : events) {
    //HTTPServeletResponse only prints out for test
    currentAktionen.getWriter().println(event.getProperty("date") + "," +   
               event.getProperty("info"));
}

It delivers all events and prints the data in my webbrowser site. --> works

But I am not able to delete such an event entity. I tried: dss.delete(key), i tried to delete during the for each loop,...

Does anybody know how to delete one or all events programatically mayby via a query? (Deleting in the Dashbord does not help me!)

Many thanks for any help!

Answer 1

I made it now, but I dont know why. The following code works now:

for (Entity event : events) {

    currentAktionen.getWriter().println(event.getProperty("date") + "," +   
           event.getProperty("info"));
    Key key = aktion.getKey();
    dss.delete(key);

}    

Dont ask me why, .... I tried this 15 times before with the last two lines of code at the beginning in the for-each and it did not work.