Spring data JPA + TABLE_PER_CLASS polymorphic save one to many

Question

I have these classes:

@Entity
@Table(name = "garage")
class Garage {

    @Id
    private String id;


    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinColumn(name = "garage_id", referencedColumnName = "id")
    private List<Vehicle> vehiclesList;
}

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
abstract class Vehicle {

}

@Entity
@Table(name = "cars")
class Car extends Vehicle {

}

@Entity
@Table(name = "trucks")
class Truck extends Vehicle {

}

I am using cascade all.

When I am trying to persist them. I get: SqlError, No table 'vehicle'

I want to clarify that I am always persisting a garage with one type of vehicles

So when I hit garageRepository.save(garage) I expect the child table (either car or truck) to be populated. and the garage_id will be the new garage.

How can this be done?

Regards, Ido

Answer 1

I believe this cannot be achieved with InheritanceType.TABLE_PER_CLASS strategy.

Reason being, with TABLE_PER_CLASS, spring-data-jpa(Hibernate) will create two tables in Database. cars and trucks. And there will be no Vehicle table.
But since you have private List<Vehicle> vehiclesList; in your Garage class, spring-data searches for Vehicle table and hence you see this error.

Couple of suggestions.

This can be achieved by.
1. InheritanceType.SINGLE_TABLE (There will be only one table. Vehicle) 2. InheritanceType.JOINED (There will be three tables cars, trucks, vehicle)

or

You can change the type in Garage to some concrete type like Car or Truck(which doesn't make sense)