Enterprise JavaBeans 3.1, 6th Edition

Table per Concrete Class

In the table per concrete class strategy, a database table is defined for each concrete class in the hierarchy. Each table has columns representing its properties and all properties of any superclasses:

CREATE TABLE "PUBLIC"."TABLEPERCLASS_PERSON"
(
   ID bigint PRIMARY KEY NOT NULL,
   FIRSTNAME varchar,
   LASTNAME varchar
)
;

CREATE TABLE "PUBLIC"."TABLEPERCLASS_CUSTOMER"
(
   ID bigint PRIMARY KEY NOT NULL,
   FIRSTNAME varchar,
   LASTNAME varchar,
   CITY varchar,
   STATE varchar,
   STREET varchar,
   ZIP varchar
)
;

CREATE TABLE "PUBLIC"."TABLEPERCLASS_EMPLOYEE"
(
   ID bigint PRIMARY KEY NOT NULL,
   FIRSTNAME varchar,
   LASTNAME varchar,
   CITY varchar,
   STATE varchar,
   STREET varchar,
   ZIP varchar,
   EMPLOYEEID integer
)
;

One major difference between this strategy and the SINGLE_TABLE strategy is that no discriminator column is needed in the database schema. Also notice that each table contains every persistent property in the hierarchy. Let’s now look at how we map this strategy with annotations:

@Entity(name = "TABLEPERCLASS_PERSON")
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class Person
{
   @Id
   @GeneratedValue(strategy = GenerationType.TABLE)
   // Cannot accept default generation strategy for table-per-class
   private Long id;

   private String firstName;
   private String lastName;
   ...
}

@Entity(name = "TABLEPERCLASS_CUSTOMER")
public class Customer extends Person
{
   private String street;
   private String city;
   private String state;
   private String zip;
   ...
}

@Entity(name = "TABLEPERCLASS_EMPLOYEE") ...