javax.persistence.PrimaryKeyJoinColumn Maven / Gradle / Ivy
// $Id: PrimaryKeyJoinColumn.java 17752 2009-10-15 01:19:21Z [email protected] $
// EJB3 Specification Copyright 2004-2009 Sun Microsystems, Inc.
package javax.persistence;
import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
/**
* Specifies a primary key column that is used as a foreign key to
* join to another table.
*
* It is used to join the primary table of an entity subclass
* in the {@link InheritanceType#JOINED JOINED} mapping strategy
* to the primary table of its superclass; it is used within a
* {@link SecondaryTable} annotation to join a secondary table
* to a primary table; and it may be used in a {@link OneToOne}
* mapping in which the primary key of the referencing entity
* is used as a foreign key to the referenced entity.
*
* If no PrimaryKeyJoinColumn annotation is
* specified for a subclass in the JOINED
* mapping strategy, the foreign key columns are assumed
* to have the same names as the primary key columns of the
* primary table of the superclass.
*
*
*
* Example: Customer and ValuedCustomer subclass
*
* @Entity
* @Table(name="CUST")
* @Inheritance(strategy=JOINED)
* @DiscriminatorValue("CUST")
* public class Customer { ... }
*
* @Entity
* @Table(name="VCUST")
* @DiscriminatorValue("VCUST")
* @PrimaryKeyJoinColumn(name="CUST_ID")
* public class ValuedCustomer extends Customer { ... }
*
*
* @see SecondaryTable
* @see Inheritance
* @see OneToOne
* @since Java Persistence 1.0
*/
@Target({ TYPE, METHOD, FIELD })
@Retention(RUNTIME)
public @interface PrimaryKeyJoinColumn {
/**
* (Optional) The name of the primary key column of the current table.
*
* Defaults to the same name as the primary key column of the primary
* table of the superclass (JOINED mapping strategy); the same
* name as the primary key column of the primary table
* (SecondaryTable mapping); or the same name as the
* primary key column for the table for the referencing entity
* (OneToOne mapping).
*/
String name() default "";
/**
* (Optional) The name of the primary key column of the table
* being joined to.
*
* Defaults to the same name as the primary key column of the primary table
* of the superclass (JOINED mapping strategy); the same name
* as the primary key column of the primary table
* (SecondaryTable mapping); or the same name as the
* primary key column for the table for the referencing entity
* (OneToOne mapping).
*/
String referencedColumnName() default "";
/**
* (Optional) The SQL fragment that is used when generating the
* DDL for the column. This should not be specified for a
* OneToOne primary key association.
*
* Defaults to the generated SQL to create a column of the inferred type.
*/
String columnDefinition() default "";
}