Question

I have 2 classes. The first class Car has a list of passengers. I need a Hibernate Criteria that will return the Car for which I have a single passenger. So something like this

class Car {

   @Id
   private Long id;
   @OneToMany
   private List<Passenger> passengers;
}

And in the Hibernate class

@Override
public Car retrieve(Passenger passenger) {
    Criteria criteria = super.createCriteria();
    criteria.add(Restrictions.eq("passengers", passenger));
    return (Car  ) criteria.uniqueResult();
}

However the below wont really work. So any suggestions how to do this

Answer 1

You need to join the Car table with the Passenger table here, which can be done with criteria API’s aliases. you should try the following:

@Override
public Car retrieve(Passenger passenger) {
    Criteria criteria = super.createCriteria();
    criteria.createAlias("passengers", "p");
    criteria.add(Restrictions.eq("p.id", passenger.getId()));
    return (Car) criteria.uniqueResult();
}

Another tip: I think that a passenger can only appear once in a car, so I would prefer Set<Passenger> instead of List<Passenger> .