@Entity
@Table(name = "foos")
public class Foo {

  @Id
  @GeneratedValue(generator = "foo-generator")
  @GenericGenerator(name = "foo-generator",
          parameters = {@Parameter(name = "min", value = "15"),
                  @Parameter(name = "max", value = "25")},
          strategy = "org.learn.domain.generator.FooGenerator")
  private String id;
}

public class FooGenerator implements IdentifierGenerator, Configurable {

  @Autowired
  private FooRepository fooRepository;

  private Integer min;
  private Integer max;

  @Override
  public Serializable generate(SessionImplementor session, Object object) throws HibernateException {
    BigInteger minId = BigInteger.TEN.pow(min - 1);
    BigInteger maxId = BigInteger.TEN.pow(max).subtract(BigInteger.ONE);

    List<String> invoiceIds = fooRepository.findFooIds();
    BigInteger currentId = invoiceIds.stream().map(BigInteger::new).max(Comparator.naturalOrder()).orElse(minId);

    if (currentId.compareTo(maxId) >= 0) {
      throw new HibernateException("ID reached max digits limit");
    }

    return maxId.add(BigInteger.valueOf(1)).toString();
  }

  @Override
  public void configure(Type type, Properties properties, ServiceRegistry serviceRegistry) throws MappingException {
    min = Integer.valueOf(properties.getProperty("min"));
    max = Integer.valueOf(properties.getProperty("max"));
  }
}

@Repository
public interface FooRepository extends JpaRepository<Foo, String> {

  @Query(value = "SELECT id FROM foos", nativeQuery = true)
  List<String> findFoosIds();
}

###
#   Database Settings
###
spring.datasource.url=jdbc:h2:mem:omniva;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE
spring.datasource.platform=h2
spring.datasource.username = sa
spring.datasource.password =
spring.datasource.driverClassName = org.h2.Driver
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.jpa.show-sql = true

###
#   H2 Settings
###
spring.h2.console.enabled=true
spring.h2.console.path=/console
spring.h2.console.settings.trace=false
spring.h2.console.settings.web-allow-others=false


###
#   Hibernate Settings
###
spring.jpa.hibernate.ddl-auto = none
spring.jpa.hibernate.use-new-id-generator-mappings=true