/*******************************************************************************
* 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;
/**
* Specifies the type of the map key for associations of type
* <code>java.util.Map</code>. The map key can be a basic type, an
* embeddable class, or an entity. If the map is specified using Java
* generics, the <code>MapKeyClass</code> annotation and associated
* type need not be specified; otherwise they must be specified.
*
* <p> The <code>MapKeyClass</code> annotation is used in conjunction
* with <code>ElementCollection</code> or one of the collection-valued
* relationship annotations (<code>OneToMany</code> or <code>ManyToMany</code>).
* The <code>MapKey</code> annotation is not used when
* <code>MapKeyClass</code> is specified and vice versa.
*
* <pre>
*
* Example 1:
*
* @Entity
* public class Item {
* @Id int id;
* ...
* @ElementCollection(targetClass=String.class)
* @MapKeyClass(String.class)
* Map images; // map from image name to image filename
* ...
* }
*
* Example 2:
*
* // MapKeyClass and target type of relationship can be defaulted
*
* @Entity
* public class Item {
* @Id int id;
* ...
* @ElementCollection
* Map<String, String> images;
* ...
* }
*
* Example 3:
*
* @Entity
* public class Company {
* @Id int id;
* ...
* @OneToMany(targetEntity=com.example.VicePresident.class)
* @MapKeyClass(com.example.Division.class)
* Map organization;
* }
*
* Example 4:
*
* // MapKeyClass and target type of relationship are defaulted
*
* @Entity
* public class Company {
* @Id int id;
* ...
* @OneToMany
* Map<Division, VicePresident> organization;
* }
*
* </pre>
* @see ElementCollection
* @see OneToMany
* @see ManyToMany
* @since Java Persistence 2.0
*/
@
Target( {
METHOD,
FIELD })
@
Retention(
RUNTIME)
public @interface
MapKeyClass {
/**(Required) The type of the map key.*/
Class value();
}