https://github.com/javaee/jpa-spec: Java(TM) Persistence API 
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

/*******************************************************************************
 * 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.

   Example:
   @Entity
   @Table(
       name="EMPLOYEE", 
       uniqueConstraints=
           @UniqueConstraint(columnNames={"EMP_ID", "EMP_NAME"})
   )
   public class Employee { ... }



Since:Java Persistence 1.0
/**
 * 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
/** (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. 
/** (Required) An array of the column names that make up the constraint. */
    String[] columnNames();
}