@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class Samplings {
    @EmbeddedId
    private EmbedddedSamplesKey id;
}

@Embeddable
public class EmbedddedSamplesKey extends AbstractId implements Serializable {

    @Column(name="year")
    private int year;

    @PrePersist
    public void prePersist() {
        year = LocalDate.now().getYear();
    }
}

@MappedSuperclass
public abstract class AbstractId {

    @Id
    @SequenceGenerator(name = "samplings_id_seq", sequenceName = "samplings_id_seq", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "samplings_id_seq")
    private Integer seq;
}