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/*
 * Copyright (c) 2008, 2023 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// Contributors:
//     Petros Splinakis - 2.2
//     Linda DeMichiel - 2.1
//     Linda DeMichiel - 2.0

package jakarta.persistence;

import java.lang.annotation.Repeatable;
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;
import static jakarta.persistence.ConstraintMode.PROVIDER_DEFAULT;

/**
 * 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 {@code PrimaryKeyJoinColumn} annotation is specified * for a subclass in the {@code 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: {@code Customer} and {@code ValuedCustomer} subclass * {@snippet : * @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 * @see ForeignKey * * @since 1.0 */ @Repeatable(PrimaryKeyJoinColumns.class) @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 ({@code JOINED} mapping * strategy); the same name as the primary key column of the * primary table ({@link SecondaryTable} mapping); or the same * name as the primary key column for the table for the * referencing entity ({@link 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 ({@code JOINED} mapping * strategy); the same name as the primary key column of the * primary table ({@link SecondaryTable} mapping); or the same * name as the primary key column for the table for the * referencing entity ({@link 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 * {@link OneToOne} primary key association. *

Defaults to the generated SQL to create a column of the * inferred type. */ String columnDefinition() default ""; /** * (Optional) A SQL fragment appended to the generated DDL * which declares this column. May not be used in * conjunction with {@link #columnDefinition()}. * * @since 3.2 */ String options() default ""; /** * (Optional) Used to specify or control the generation of a * foreign key constraint for the primary key join column * when table generation is in effect. If this element is not * specified, the persistence provider's default foreign key * strategy will apply. * * @since 2.1 */ ForeignKey foreignKey() default @ForeignKey(PROVIDER_DEFAULT); }





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