Question

I am using objectify 3.1 on appengine and attempting to do a ancestor query. I want to fetch all the children of an object that are of a certain kind. Below is my code:

@Cached
@Entity
public class Car {

 @Id
 @GeneratedValue(strategy = GenerationType.IDENTITY)
 private Long id;

 private String make;
 private String model;

}

@Cached
@Entity
public class Tire {

@Id
public String keyName; 


@Parent Key<Car> car;

private String brand;
private String size;

}

My query is this code:

        List<Tire> list= ofy.query(Tire.class).ancestor(new    Key<Car(Car.class,carID))).list();

When I create the tire objects I use this code to set the relationship:

        newTire.setCar(new Key<Car>(Car.class,Car.getID()));

I know the Parent relationship is there because I can query for it in the datastore admin and it shows the parent in the decoded entity key:

Decoded entity key: Car: id=135172 > Tire: name=myCarUniqueID

This query always returns 0 results, and it seems like I have followed all the best practices on the objectify website. Any help would be appreciated!

Answer 1

Your code looks ok, so the only thing that might be wrong is a non-existing carID.

The Objectify javadoc listed on the site is actually for trunk version which is a forthcoming Objectify 4. What you need to look at is Objectify 3.1 javadoc: this version has fetch() on the query.

Also, @GeneratedValue is not an Objectify annotation.