javax.persistence.MapKeyClass Maven / Gradle / Ivy
/*
* Copyright (c) 2008, 2019 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0,
* or the Eclipse Distribution License v. 1.0 which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
*/
// Contributors:
// Linda DeMichiel - 2.1
// Linda DeMichiel - 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
* java.util.Map. The map key can be a basic type, an
* embeddable class, or an entity. If the map is specified using Java
* generics, the MapKeyClass annotation and associated
* type need not be specified; otherwise they must be specified.
*
* The MapKeyClass annotation is used in conjunction
* with ElementCollection or one of the collection-valued
* relationship annotations (OneToMany or ManyToMany).
* The MapKey annotation is not used when
* MapKeyClass is specified and vice versa.
*
*
*
* 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;
* }
*
*
* @see ElementCollection
* @see OneToMany
* @see ManyToMany
* @since 2.0
*/
@Target( { METHOD, FIELD })
@Retention(RUNTIME)
public @interface MapKeyClass {
/**(Required) The type of the map key.*/
Class value();
}