@Entity
@Table(name = "Groups")
@Name(value = "group")
public class Group implements Serializable
{
	@EmbeddedId
	private GroupId embeddedId;

	...
}

@Embeddable
public class GroupId implements Serializable
{
	@Column(name = "round_id")
	private Integer roundId;

	@Column(name = "ordinal_nbr")
	private Integer ordinalNbr = 1;

	...
}