EntitySubclass对象化查询

Question

I am using Google App Engine (Java) with Objectify 4.0b3 and want to have a superclass Facility with the child classes SportFacility and UserDefinedFacility . I want to be able to query for Facility by id and thereby get Facilities from all child classes and I also want to be able to do the same for each of the child classes.

@Entity
public class Facility {

    @Id
    protected Long id;
    @Index
    protected String name;
    @Index
    protected double x_coordinate;
    @Index
    protected double y_coordinate;
    @Index
    protected String address;

    protected Facility(){}

    public Facility(String name, double x_coordinate, double y_coordinate, String address) {
        this.name = name;
        this.x_coordinate = x_coordinate;
        this.y_coordinate = y_coordinate;
        this.address = address;
}

@EntitySubclass(index=true)
public class SportFacility extends Facility{

    @Index
    private String url;

    private void SportFacility(){}

    public SportFacility(String name, double x_coordinate, double y_coordinate, String address, String url) {
        super(name, x_coordinate, y_coordinate, address);
        this.url = url;
    }
}


@EntitySubclass(index=true)
public class UserDefinedFacility extends Facility{

    @Index
    private String url;

    private void UserDefinedFacility(){}

    public UserDefinedFacility(String name, double x_coordinate, double y_coordinate, String address) {
        super(name, x_coordinate, y_coordinate, address);

    }
}

Basically my problem is the same as described in Entity hierarchies in Objectify 4.0 but in my case the query

Facility facility = ofy().load().type(Facility.class).id(id);

does not work because AndroidStudio complains that the type should be

LoadResult<Facility> 

instead of Facility.

Since the syntax of inheritance concepts seems to change often between Objectify versions, I couldn't find a working solution, so I'd really appreciate any help!

Thanks in advance

Samuel

Answer 1

Android Studio is correct; to get the entity itself, you want either:

Facility facility = ofy().load().type(Facility.class).id(id).now();

or

Facility facility = ofy().load().type(Facility.class).id(id).safe();

The latter will throw a NotFoundException if the entity does not exist (now would return null as I recall).