@Embeddable
public class EmbeddableData implements Serializable {

  @Column(name = "DATA_X", nullable = false)
  private double x;

  @Column(name = "DATA_Y", nullable = false)
  private double y;
  ...
}

@Entity
public class EntityA implements Serializable {

  private static final long serialVersionUID = 1L;

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  @Column(name = "ID")
  private long id;

  @CollectionTable(name = "DATA_TABLE", joinColumns = @JoinColumn(name = "ENTITY_FK", nullable = false))
  @ElementCollection
  @OrderColumn(name = "ARRAY_INDEX", nullable = false)
  private List<EmbeddableData> data;
  ...
}