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//$Id: PrimaryKeyJoinColumn.java 11282 2007-03-14 22:05:59Z epbernard $

//EJB3 Specification Copyright 2004-2006 Sun Microsystems, Inc.

package javax.persistence;

import java.lang.annotation.Retention;

import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.*;

import static java.lang.annotation.RetentionPolicy.*;

/**

 * This annotation 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 JOINED mapping strategy to

 * the primary table of its superclass; it is used within a SecondaryTable annotation to join a

 * secondary table to a primary table; and it may be used in a 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

 *

 * @author Emmanuel Bernard

 */

@Target({TYPE, METHOD, FIELD}) @Retention(RUNTIME)

public @interface PrimaryKeyJoinColumn {

        /**

         * 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 "";

        /**

         * 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 "";

        /**

         * 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 "";

}