JPA/Hibernate: not creating foreign keys even though I used @Inheritance(strategy = InheritanceType.JOINED)

Question

I have a super abstract class User:

package com.Abdelouadoud.MoroccoCraftsAPI.model.User;

import com.Abdelouadoud.MoroccoCraftsAPI.model.Adress;
import com.Abdelouadoud.MoroccoCraftsAPI.model.UserRole;
import jakarta.persistence.*;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.ArrayList;
import java.util.List;

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@Data
@AllArgsConstructor
@NoArgsConstructor
@Table(name = "users")
public abstract class User {

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

    private String firstName;
    private String lastName;
    private String email;
    private String password;

    @Enumerated(EnumType.STRING)
    private UserRole userRole;

    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Adress> adressList = new ArrayList<>();

    public User(User user) {
        this.id = user.id;
        this.firstName = user.firstName;
        this.lastName = user.lastName;
        this.email = user.email;
        this.password = user.password;
        this.userRole = user.userRole;
        this.adressList = new ArrayList<>(user.adressList);
    }
}

and a Customer class that inherits from it:

package com.Abdelouadoud.MoroccoCraftsAPI.model.User;

import com.Abdelouadoud.MoroccoCraftsAPI.model.Order;
import com.Abdelouadoud.MoroccoCraftsAPI.model.Product;
import com.Abdelouadoud.MoroccoCraftsAPI.model.Store;
import com.fasterxml.jackson.annotation.JsonIgnore;
import jakarta.persistence.CascadeType;
import jakarta.persistence.Entity;
import jakarta.persistence.OneToMany;
import jakarta.persistence.Table;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.ArrayList;
import java.util.List;

@Entity
@Data
@AllArgsConstructor
@NoArgsConstructor
@Table(name = "customers")
public class Customer extends User{

    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Store> favoriteStores = new ArrayList<>();

    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Product> favoriteProducts = new ArrayList<>();

    @OneToMany //A list of orders contain many orders 1-* relation
    private List<Order> orders = new ArrayList<>();

    public Customer(User user) {
        super(user);
    }
}

and finally an other Seller class that inherits from Customer:

package com.Abdelouadoud.MoroccoCraftsAPI.model.User;

import com.Abdelouadoud.MoroccoCraftsAPI.model.Store;
import jakarta.persistence.CascadeType;
import jakarta.persistence.Entity;
import jakarta.persistence.OneToMany;
import jakarta.persistence.Table;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.ArrayList;
import java.util.List;

@Entity
@Data
@AllArgsConstructor
@NoArgsConstructor
@Table(name = "sellers")
public class Seller extends Customer{


    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Store> storeList = new ArrayList<>();
}

the problem is that after executing the code, hibernate doesn't create foreign keys towards the super classes even though I used the annotation @Inheritance(strategy = InheritanceType.JOINED):

Hibernate: create table customers (id bigint not null, primary key (id)) engine=InnoDB

Hibernate: create table sellers (id bigint not null, primary key (id)) engine=InnoDB

I dropped the data base and recreated it, then reran the code but the problem persisted.

I need your help!

Answer 1

Hibernate will not create an additional column with foreign key. Each table will have an id column and all IDs will be equal for the same record. There will be a constraint generated for this reason. You should see it in the logs.