jakarta.persistence.MapKeyClass Maven / Gradle / Ivy
/*
* Copyright (c) 2008, 2023 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 jakarta.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
* {@link 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 {@code MapKeyClass} annotation and associated
* type need not be specified; otherwise they must be specified.
*
* The {@code MapKeyClass} annotation is used in conjunction
* with {@link ElementCollection} or one of the collection-valued
* relationship annotations ({@link OneToMany} or {@link ManyToMany}).
* The {@link MapKey} annotation is not used when {@code MapKeyClass}
* is specified and vice versa.
*
*
Example 1:
* {@snippet :
* @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:
* {@snippet :
* // MapKeyClass and target type of relationship can be defaulted
*
* @Entity
* public class Item {
* @Id
* int id;
* ...
* @ElementCollection
* Map images;
* ...
* }
* }
*
* Example 3:
* {@snippet :
* @Entity
* public class Company {
* @Id
* int id;
* ...
* @OneToMany(targetEntity = com.example.VicePresident.class)
* @MapKeyClass(com.example.Division.class)
* Map organization;
* }
* }
*
*
Example 4:
* {@snippet :
* // MapKeyClass and target type of relationship are defaulted
*
* @Entity
* public class Company {
* @Id
* int id;
* ...
* @OneToMany
* Map 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();
}