/*
 * Copyright (c) 2008, 2009, 2011 Oracle, Inc. 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.
 */
package javax.persistence;

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

Applied to a persistent field or property of an entity class or mapped superclass to denote a composite primary key that is an embeddable class. The embeddable class must be annotated as Embeddable. 

 There must be only one EmbeddedId annotation and
no Id annotation when the EmbeddedId annotation is used.

 The AttributeOverride annotation may be used to override the column mappings declared within the embeddable class. 

 The MapsId annotation may be used in conjunction with the EmbeddedId annotation to specify a derived
primary key.

 If the entity has a derived primary key, the
AttributeOverride annotation may only be used to
override those attributes of the embedded id that do not correspond
to the relationship to the parent entity.

 Relationship mappings defined within an embedded id class are not supported.

   Example 1:
   @EmbeddedId
   protected EmployeePK empPK;
   Example 2:
   @Embeddable
   public class DependentId {
      String name;
      EmployeeId empPK;   // corresponds to primary key type of Employee
   }
   @Entity
   public class Dependent {
      // default column name for "name" attribute is overridden
      @AttributeOverride(name="name", @Column(name="dep_name"))
      @EmbeddedId DependentId id;
      ...
      @MapsId("empPK")
      @ManyToOne Employee emp;
   }

See Also:
Embeddable
MapsId
Since:
Java Persistence 1.0/**
 * Applied to a persistent field or property of an entity
 * class or mapped superclass to denote a composite primary
 * key that is an embeddable class. The embeddable class
 * must be annotated as {@link Embeddable}.
 * <p>
 * <p> There must be only one <code>EmbeddedId</code> annotation and
 * no <code>Id</code> annotation when the <code>EmbeddedId</code> annotation is used.
 * <p>
 * <p> The {@link AttributeOverride} annotation may be used to override
 * the column mappings declared within the embeddable class.
 * <p>
 * <p> The {@link MapsId} annotation may be used in conjunction
 * with the <code>EmbeddedId</code> annotation to specify a derived
 * primary key.
 * <p>
 * <p> If the entity has a derived primary key, the
 * <code>AttributeOverride</code> annotation may only be used to
 * override those attributes of the embedded id that do not correspond
 * to the relationship to the parent entity.
 * <p>
 * <p> Relationship mappings defined within an embedded id class are not supported.
 * <p>
 * <pre>
 *    Example 1:
 *
 *    &#064;EmbeddedId
 *    protected EmployeePK empPK;
 *
 *
 *    Example 2:
 *
 *    &#064;Embeddable
 *    public class DependentId {
 *       String name;
 *       EmployeeId empPK;   // corresponds to primary key type of Employee
 *    }
 *
 *    &#064;Entity
 *    public class Dependent {
 *       // default column name for "name" attribute is overridden
 *       &#064;AttributeOverride(name="name", &#064;Column(name="dep_name"))
 *       &#064;EmbeddedId DependentId id;
 *       ...
 *       &#064;MapsId("empPK")
 *       &#064;ManyToOne Employee emp;
 *    }
 * </pre>
 *
 * @see Embeddable
 * @see MapsId
 * @since Java Persistence 1.0
 */
@Target({FIELD})
@Retention(RUNTIME)
public @interface EmbeddedId {
}