Question

I’m using Java & GAE datastore to store, manage and retrieve some data for my application.

Basically I have two classes: Customer and Store. The idea is that one customer can have more than one store associated, and many customers can exist.

The structure of a customer is something like this:

<Customer>
   <id>id1</id>
       <Stores>
           <Store>
               <storeId>100</storeId>
               <city>Venice</city>
           </Store>
           <Store>
                <storeId>200</storeId>
                <city>Milan</city>
           </Store>
           <Store>
                <storeId>300</storeId>
                <city>Venice</city>
           </Store>
       </Stores>
 </Customer>

As I said before, there can be MANY customers:

<Customers>
    <Customer>
       ...
    </Customer>
    <Customer>
       ...
    </Customer>
</Customers>

I need to build a filter to get only a portion of these customers, passing to a query a “CITY” parameter:
For example, if I want to show Customers that has at least one Store located in Venice, I would do something like ( just to give you the idea)

GET Customer WHERE Customer.Store.City = 'Venice'

What I’d like to get is every Customer that has a Store located in a particular city.. but also, the Customer Object needs to have those stores! like this:

<Customer>
    <id>id1</id>
       <Stores>
           <Store>
               <storeId>100</storeId>
               <city>Venice</city>
           </Store>
           <Store>
               <storeId>300</storeId>
               <city>Venice</city>
           </Store>
        </Stores>
</Customer>
<Customer>
    <id>id2</id>
       <Stores>
           <Store>
               <storeId>700</storeId>
               <city>Venice</city>
           </Store>
        </Stores>
</Customer>

I can get those stores correctly, but I need to find a way to connect every store to his ancestor customer..

String city = 'something';
Query query = mgr.newQuery(Store.class, "city == '"+city+"' ");
List<Store> oggetti = (List<Store>) query.execute();

Any idea on how to do this?

I hope I was clear enough.. thanks in advance, best regards

---

Additional info:

class Customer:

@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable = "true")
@Cacheable("false")
@FetchGroup(name="customerstores", members={@Persistent(name="storeList")})
public class Customer {

    @PrimaryKey
@Persistent
private String id= "";

    @Persistent
    @Unowned
private List<Store> storeList;

    //getters and setters here
    ....
}

Class Store:

@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable = "true")
@Cacheable("false")
public class Store {

    @PrimaryKey
@Persistent
private String storeUniqueKey = "";

    @Persistent
    private String city = "";

    //getters and setters here
    ....
}

Answer 1

See if following code could fit your requirement.

Query query = pm.newQuery(Customer.class);
query.declareVariables("Customer store");
query.setFilter(
    "this.stores.contains(store) && store.city == \"SomeCity\"");
Collection result = (Collection)query.execute();