Question

Suppose I have 2 models

Public class Bus extends Model{

    @OneToMany(mappedBy="bus")
    private List<Passenger> passengers;

    public Bus(passengers){
        this.passengers=passengers;
    }

    public List<Passenger> getPassengers(){
        return passengers;
    }
}

public Class Passenger extends Model{

    @ManyToOne
    private Bus bus;

    public Passenger(Bus bus){
        this.bus=bus;
    }
}

Can I use a controller method that finds all the passengers in a bus using the getter. eg:

public static void getPassengers(Long busId){
    Bus bus = Bus.findById(busId);
    List<Passengers> pList = bus.getPassengers();
}

I tried it in a real play web application but the List size returned is always 0.

Thanks in advance.

Answer 1

Can I use a controller method that finds all the passengers in a bus using the getter?

Yes, you can. But I think the problem isn’t using a getter, it is that you have not constructed your models correctly.

There are 3 problems I see in your example:

1. In your controller action getPassengers(Long busId) you need to change List<Passengers> to List<Passenger> (singular “Passenger”)

2. In your Bus model class, you need to either make passengers public or declare a public setter. The “Play!” way is to just declare fields as public and let the framework generate the getters and setters for you. The only reason you would declare your own getters and setters is if you needed to add some logic.

3. In your Passenger model class, you need to make bus public.

Here’s how I would fix your code:

public class Bus extends Model{

    @OneToMany(mappedBy="bus")
    public List<Passenger> passengers;

    public Bus(passengers){
        this.passengers=passengers;
    }

    // No need for getters or setters, but we'll add a getter for the sake of this question:
    public List<Passenger> getPassengers() {
        return this.passengers;
    }
}

public class Passenger extends Model{

    @ManyToOne
    public Bus bus;

    public Passenger(Bus bus){
        this.bus = bus;
    }
}

And your controller action:

public static void getPassengers(Long busId){
    Bus bus = Bus.findById(busId);
    List<Passenger> pList = bus.getPassengers();
    render(pList); // or whatever rendering you want to do
}

If this doesn’t fix your problem, then you are not loading your data correctly. You should post the code you are running to actually create the records – whether that be loading a YAML file or whatever.