| /* |
| * Copyright (c) 2008, 2018 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 - 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 map key for associations of type |
| * {@link java.util.Map java.util.Map} when the map key is itself the primary |
| * key or a persistent field or property of the entity that is |
| * the value of the map. |
| * |
| * <p> 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. |
| * |
| * <p> The {@link MapKeyClass} annotation is not used when |
| * <code>MapKey</code> is specified and vice versa. |
| * |
| * <pre> |
| * |
| * Example 1: |
| * |
| * @Entity |
| * public class Department { |
| * ... |
| * @OneToMany(mappedBy="department") |
| * @MapKey // map key is primary key |
| * public Map<Integer, Employee> 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="name") |
| * public Map<String, Employee> getEmployees() {... } |
| * ... |
| * } |
| * |
| * @Entity |
| * public class Employee { |
| * @Id public Integer getEmpId() { ... } |
| * ... |
| * @ManyToOne |
| * @JoinColumn(name="dept_id") |
| * public Department getDepartment() { ... } |
| * ... |
| * } |
| * </pre> |
| * |
| * @since Java Persistence 1.0 |
| */ |
| @Target({METHOD, FIELD}) |
| @Retention(RUNTIME) |
| public @interface MapKey { |
| |
| /** |
| * (Optional) The name of the persistent field or property of the |
| * associated entity that is used as the map key. |
| * <p> Default: If the |
| * <code>name</code> 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 <code>IdClass</code>, an instance of the primary key |
| * class is used as the key. |
| */ |
| String name() default ""; |
| } |