/*******************************************************************************
 * 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.RetentionPolicy.RUNTIME;

/**
 * Specifies that a unique constraint is to be included in
 * the generated DDL for a primary or secondary table.
 *
 * <pre>
 *    Example:
 *    &#064;Entity
 *    &#064;Table(
 *        name="EMPLOYEE", 
 *        uniqueConstraints=
 *            &#064;UniqueConstraint(columnNames={"EMP_ID", "EMP_NAME"})
 *    )
 *    public class Employee { ... }
 * </pre>
 *
 * @since Java Persistence 1.0
 */
@Target({}) 
@Retention(RUNTIME)
public @interface UniqueConstraint {

    /** (Optional) Constraint name.  A provider-chosen name will be chosen
     * if a name is not specified.
     *
     * @since Java Persistence 2.0
     */
    String name() default "";

    /** (Required) An array of the column names that make up the constraint. */
    String[] columnNames();
}
