@MappedSuperclass
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public static class AbstractEntity {

	@Id
	private Long id;

	@Column(name = "code", nullable = false, unique = true)
	private String code;

	public Long getId() {
		return id;
	}

	public void setId(Long id) {
		this.id = id;
	}

	public String getCode() {
		return code;
	}

	public void setCode(String code) {
		this.code = code;
	}

}

@Entity(name = "Category")
public static class CategoryEntity extends AbstractEntity {

}

@Entity(name = "Taxon")
@Table(name = "taxon", uniqueConstraints = @UniqueConstraint(columnNames = { "catalog_version_id", "code" }))
@AttributeOverride(name = "code", column = @Column(name = "code", nullable = false, unique = false))
public static class TaxonEntity extends CategoryEntity {

	@Column(name = "catalog_version_id")
	private String catalogVersion;

	public String getCatalogVersion() {
		return catalogVersion;
	}

	public void setCatalogVersion(String catalogVersion) {
		this.catalogVersion = catalogVersion;
	}
}