Spring Data JPA (Postgres) - Insert into One table, reading the foreign key from a table that contains static data

Question

I am currently working with Spring Data JPA, specifically Postgres. Our database is highly Normalized. In some scenarios we have some tables that contains static data. In that case if I am going to insert into table address for example and table address_type contains the static data, I would need to insert the Primary Key of table address_type in a column of table address, to make a Foreign Key reference from table address to table address_type(static data).

Example:

Database Code

create table address_type(
    id Serial Primary Key,
    type char(3),
    description (100)
);
insert into address_type(id, type, description) values(1, 'PRIMARY', 'Primary description');
insert into address_type(id, type, description) values(2, 'SECONDARY', 'Secondary description');

Relation (1 - N)

create table address(
   id Serial Primary Key,
   address varchar(50) not null,
   address_type_id integer references address_type(id)
);
insert into address(id, address, address_type) values(1, 'address somewhere 1', 1);
insert into address(id, address, address_type) values(2, 'address somewhere 2', 1);
insert into address(id, address, address_type) values(3, 'address somewhere 3', 2);

---

Spring Data JPA Code

@Table(name = "address_type")
public class AddressType {
   
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private Long id;

   @Column(name = "type")
   private String type;

   @Column(name = "description")
   private String description;

   @OneToMany(mappedBy = "addressType")
   private Address address;

   // Getters and Setters (Lombok)
}

@Table(name = "address")
public class Address {
   
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private Long id;

   @Column(name = "type")
   private String address;

   @Column(name = "address_type_id")
   @JoinColumn(---> logic?????????? <-----)
   @ManyToOne(---> logic?????????? <-----)
   private AddressType addressType;

   // Getters and Setters (Lombok)
}

I guess my question is how should I need to setup the logic inside the @JoinColumn and @ManyToOne annotations in the Address entity?

P.D. The Insert should only happen in table address, Spring Data should only read from table address_type to get the foreign key to be stored in the address table.

Answer 1

I got the answer after a lot of research and try/error.

The configuration inside the annotations are the following:

In class Address

    @Column(name = "address_type_id")
    @ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinColumn(name = "address_type_id", referencedColumnName = "id")
    private AddressType addressType;

Then in AddressType, you should always have a mapped by reference to the child table.

   @OneToMany(mappedBy = "addressType")
   private Address address;

One IMPORTANT thing to remember, is that before saving back to the database, you should fetch in the database for the entity you want to refer in your child table, so that Spring Data JPA recognize that this is NOT a new record in AddressType table, BUT just a reference and saves the foreign key in the Address table.