Identifier restricted to String or UUID

[dschulten]

I have experimented with an Integer as Identifier:

public class Thing
    implements AggregateRoot<Thing, ThingIdentifier> {

  @Id private Thingdentifier id;

  public record ThingIdentifier(Integer id) implements Identifier, Serializable {
    public static ThingIdentifier of(Integer id) {
      return new ThingIdentifier(id);
    }
  }
}

PrimitivesToIdentifierConverter and IdentifierToPrimitivesConverter only appear to accept String and UUID:

private static final Set<Class<?>> DEFAULT_PRIMITIVES = new HashSet<>(Arrays.asList(String.class, UUID.class));

What is the reason that an Integer is not an accepted identifier? Is it possible to use an Integer wrapped into an Identifier?

[odrotbohm]

The desire for numeric identifiers usually stems from database-generated identifiers. Those in turn are not a good fit for domain models, as they require a roundtrip to the database to establish identity. A UUID instance can reliably be created in application code. What would be the source of your numeric value?

[sivaprasadreddy]

I tried using db-generated sequence values wrapped in a Value object as Identifier and faced some challenges(jakartaee/persistence#207). Finally decided to use an application generated identifier like UUID or TSID (https://github.com/vladmihalcea/hypersistence-tsid).

[dschulten]

The source of the numeric identifiers are domain classes with an @Id bound to an auto increment column in a CRUD spring-data-rest module (for settings) which is part of a larger modulith with DDD modules, that reference the settings by their IDs.

The settings module has no domain logic, it's CRUD. Hence it seemed appropriate to build them as a Spring Data Rest module as part of a modulith.

The Getting Started chapter https://docs.spring.io/spring-data/rest/reference/introduction/getting-started.html (jpa) lead me down the road of using auto incremented ids:

@Entity
class Person {

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