javax.persistence.MapKey Maven / Gradle / Ivy
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can obtain
* a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
* or glassfish/bootstrap/legal/LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
* Sun designates this particular file as subject to the "Classpath" exception
* as provided by Sun in the GPL Version 2 section of the License file that
* accompanied this code. If applicable, add the following below the License
* Header, with the fields enclosed by brackets [] replaced by your own
* identifying information: "Portions Copyrighted [year]
* [name of copyright owner]"
*
* Contributor(s):
*
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/
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;
/**
* Is used to specify the map key for associations of type
* {@link java.util.Map}.
*
* If a persistent field or property other than the primary
* key is used as a map key then it is expected to have a
* uniqueness constraint associated with it.
*
*
*
* Example 1:
*
* @Entity
* public class Department {
* ...
* @OneToMany(mappedBy="department")
* @MapKey(name="empId")
* public Map getEmployees() {... }
* ...
* }
*
* @Entity
* public class Employee {
* ...
* @Id Integer getEmpid() { ... }
* @ManyToOne
* @JoinColumn(name="dept_id")
* public Department getDepartment() { ... }
* ...
* }
*
* Example 2:
*
* @Entity
* public class Department {
* ...
* @OneToMany(mappedBy="department")
* @MapKey(name="empPK")
* public Map getEmployees() {... }
* ...
* }
*
* @Entity
* public class Employee {
* @EmbeddedId public EmployeePK getEmpPK() { ... }
* ...
* @ManyToOne
* @JoinColumn(name="dept_id")
* public Department getDepartment() { ... }
* ...
* }
*
* @Embeddable
* public class EmployeePK {
* String name;
* Date bday;
* }
*
*
* @since Java Persistence 1.0
*/
@Target({METHOD, FIELD})
@Retention(RUNTIME)
public @interface MapKey {
/**
* The name of the persistent field or property of the
* associated entity that is used as the map key. If the
* name element is not specified, the primary key of the
* associated entity is used as the map key. If the
* primary key is a composite primary key and is mapped
* as {@link IdClass}, an instance of the primary key
* class is used as the key.
*/
String name() default "";
}