JPA entities - EJB 3 in Action - page 341

Mapping an entity to a single table
@Table specifies the table containing the columns to which the entity is mapped. The
name parameter is most important. By default all the persistent data for the entity is
mapped to the table specified by the annotation's name parameter. As you can see from the
annotation's definition, it contains a few other parameters:
@Target(TYPE)
@Retention(RUNTIME)
public @interface Table {
String name() default "";
String catalog() default "";
String schema() default "";
Index[] indexes() default {};
UniqueConstraint[] uniqueConstraints() default {};
}
The @Table annotation is optional. By default, JPA will assume the name of the table is
the name of the @Entity class itself. In the case of the Category class in listing 9.1 ,
JPA will assume the name of the database table is Category . The @Table annotation
allows you to override this conventional behavior. For example, if the database table is
named ITEM_CATEGORY , use the @Table annotation to configure JPA:
@Table(name="ITEM_CATEGORY")
public class Category
The catalog and schema elements are there if you need to further specify the location
of the table in the database. Schemas and catalogs are common database features and will
not be discussed further. But as an example, suppose the ITEM_CATEGORY table was in
the ACTIONBAZAAR schema. Use the schema parameter to configure JPA:
@Table(name="ITEM_CATEGORY", schema="ACTIONBAZAAR"))
public class Category
The catalog and schema elements aren't commonly used because those details are usu-
ally part of the data source configuration on your Java EE server. It's typically bad practice
for your code to know too much about the database because changes would require a re-
build of your code instead of a reconfiguration of the EE server.