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/*******************************************************************************
 * Copyright (c) 2008 - 2013 Oracle Corporation. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Linda DeMichiel - Java Persistence 2.1
 *     Linda DeMichiel - Java Persistence 2.0
 *
 ******************************************************************************/
package javax.persistence;

import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import static javax.persistence.ConstraintMode.PROVIDER_DEFAULT;

/**
 * Specifies the mapping for composite foreign keys. This annotation 
 * groups JoinColumn annotations for the same relationship.
 *
 *  When the JoinColumns annotation is used, 
 * both the name and the referencedColumnName elements 
 * must be specified in each such JoinColumn annotation.
 *
 * 
 *
 *    Example:
 *    @ManyToOne
 *    @JoinColumns({
 *        @JoinColumn(name="ADDR_ID", referencedColumnName="ID"),
 *        @JoinColumn(name="ADDR_ZIP", referencedColumnName="ZIP")
 *    })
 *    public Address getAddress() { return address; }
 * 
 *
 * @see JoinColumn
 * @see ForeignKey
 *
 * @since Java Persistence 1.0
 */
@Target({METHOD, FIELD}) 
@Retention(RUNTIME)
public @interface JoinColumns {

    /**
     * The join columns that map the relationship.
     */
    JoinColumn[] value();

    /**
     *  (Optional) Used to specify or control the generation of a
     *  foreign key constraint when table generation is in effect. 
     *  If both this element and the foreignKey element 
     *  of any of the JoinColumn elements are specified, 
     *  the behavior is undefined.  If no foreign key annotation element
     *  is specified in either location, the persistence provider's
     *  default foreign key strategy will apply.
     *
     *  @since Java Persistence 2.1
     */
    ForeignKey foreignKey() default @ForeignKey(PROVIDER_DEFAULT);
}