Java Reference
In-Depth Information
Bidder
to
BIDDERS
. The following listing shows how to configure JPA using the joined-
tables strategy.
Listing 9.22. Joined-tables strategy
This listing shows the
@DiscriminatorColumn
and
@DiscriminatorValue
annotations used in exactly the same way as the single-table strategy. The
@In-
heritance
annotation's strategy element is specified as
JOINED
. In addition, the one-
to-one relationships between parent and child tables are implemented through the
@PrimaryKeyJoinColumn
annotations in both the
Bidder
and
Seller
entities. In both cases, the
name
element specifies that
BIDDER.USER_ID
and
SELLER.USER_ID
are foreign keys back to
USER.USER_ID
.
Bidder
and
Seller
also use
@Table
to specify which table they map to (
and
).
The joined-tables strategy is probably the best mapping choice from a design perspective.
From a performance perspective, it's worse than the single-table strategy because it re-
quires the joining of multiple tables for polymorphic queries.
