Is it possible to have "multiple levels" of inheritance?
Consider: Location -> Point -> AbsolutePoint -> GeographicPoint
Using joinded inheritance the discriminator "accumulates", eg:
Relative to Location, Point has just one discriminator "PT", for
AbsolutePoint there is "ABS" relative to Point and "PT" relative to
Location. Tables and classes follow.
(thanks)
"public.loc"
----------+---------------+-----------
loc_id | numeric(20,0) | not null
cat_code | character(6) | not null
----------+---------------+-----------
"loc_pkey" PRIMARY KEY, btree (loc_id)
"fk_loc_cat_code" FOREIGN KEY (cat_code) REFERENCES loc_cat_code(code)
"public.point"
----------+---------------+-----------
point_id | numeric(20,0) | not null
cat_code | character(6) | not null
----------+---------------+-----------
"point_pkey" PRIMARY KEY, btree (point_id)
"fk_point_cat_code" FOREIGN KEY (cat_code) REFERENCES point_cat_code(code)
"point_point_id_fkey" FOREIGN KEY (point_id) REFERENCES loc(loc_id)
"public.abs_point"
-----------------------+---------------+-----------------------
abs_point_id | numeric(20,0) | not null
cat_code | character(6) | not null
abs_point_ver_dist_id | numeric(20,0) | default NULL::numeric
-----------------------+---------------+-----------------------
"abs_point_pkey" PRIMARY KEY, btree (abs_point_id)
"fk_point_cat_code" FOREIGN KEY (cat_code) REFERENCES
abs_point_cat_code(code)
"fk_point_id" FOREIGN KEY (abs_point_id) REFERENCES point(point_id)
"public.geo_point"
---------------------+---------------+----------------------
geo_point_id | numeric(20,0) | not null
lat_coord | numeric(9,6) | not null
long_coord | numeric(10,6) | not null
lat_precision_code | character(6) | default NULL::bpchar
long_precision_code | character(6) | default NULL::bpchar
---------------------+---------------+----------------------
"geo_point_pkey" PRIMARY KEY, btree (geo_point_id)
"geo_point_geo_point_id_fkey" FOREIGN KEY (geo_point_id) REFERENCES
abs_point(abs_point_id)
@Entity
@Table(name = "loc")
@Inheritance(strategy = InheritanceType.JOINED)
@DiscriminatorColumn(name = "cat_code", discriminatorType =
DiscriminatorType.STRING, length = 6)
@DiscriminatorValue("LOC ")
@XmlRootElement
@XmlSeeAlso({Point.class})
public class Location implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@Basic(optional = false, fetch = FetchType.EAGER)
@NotNull
@Column(name = "loc_id", precision = 20, scale = 0)
private BigDecimal locId;
@ManyToOne(fetch = FetchType.EAGER, optional = true)
@JoinColumn(name = "cat_code")
protected LocationCategory locationCategory;
// ...
}
@Entity
@Table(name = "point")
@DiscriminatorValue("PT ")
@PrimaryKeyJoinColumn(name = "point_id", referencedColumnName = "loc_id")
@Inheritance(strategy = InheritanceType.JOINED)
@DiscriminatorColumn(name = "cat_code", discriminatorType =
DiscriminatorType.STRING, length = 6)
@XmlRootElement
@XmlSeeAlso({AbsolutePoint.class})
public class Point extends Location implements Serializable {
@ManyToOne(optional = true, fetch = FetchType.EAGER)
@JoinColumn(name = "cat_code")
private PointCategory pointCategory;
// ...
}
@Entity
@Table(name = "abs_point")
@DiscriminatorValue("ABS ")
@PrimaryKeyJoinColumn(name="abs_point_id", referencedColumnName="point_id")
@Inheritance(strategy = InheritanceType.JOINED)
@DiscriminatorColumn(name = "cat_code",
discriminatorType=DiscriminatorType.STRING, length = 6)
@XmlRootElement
@XmlSeeAlso({GeographicPoint.class})
public class AbsolutePoint extends Point implements Serializable {
@ManyToOne(fetch = FetchType.EAGER, optional = true)
@JoinColumn(name = "cat_code")
private AbsolutePointCategory absPointCategory;
// ...
}
@Entity
@Table(name = "geo_point")
@DiscriminatorValue("GEOGPT")
@PrimaryKeyJoinColumn(name="geo_point_id",
referencedColumnName="abs_point_id")
@XmlRootElement
public class GeographicPoint extends AbsolutePoint implements Serializable {
private static final long serialVersionUID = 1L;
@Basic(optional = false)
@NotNull
@Column(name = "lat_coord", precision=9, scale=6)
private BigDecimal latCoord;
// ...
}
