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Java > Open Source Codes > javax > persistence > MapKey


1 /*
2  * The contents of this file are subject to the terms
3  * of the Common Development and Distribution License
4  * (the License). You may not use this file except in
5  * compliance with the License.
6  *
7  * You can obtain a copy of the license at
8  * https://glassfish.dev.java.net/public/CDDLv1.0.html or
9  * glassfish/bootstrap/legal/CDDLv1.0.txt.
10  * See the License for the specific language governing
11  * permissions and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL
14  * Header Notice in each file and include the License file
15  * at glassfish/bootstrap/legal/CDDLv1.0.txt.
16  * If applicable, add the following below the CDDL Header,
17  * with the fields enclosed by brackets [] replaced by
18  * you own identifying information:
19  * "Portions Copyrighted [year] [name of copyright owner]"
20  *
21  * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
22  */

23 package javax.persistence;
24
25 import java.lang.annotation.Target JavaDoc;
26 import java.lang.annotation.Retention JavaDoc;
27 import static java.lang.annotation.ElementType.FIELD JavaDoc;
28 import static java.lang.annotation.ElementType.METHOD JavaDoc;
29 import static java.lang.annotation.RetentionPolicy.RUNTIME JavaDoc;
30
31 /**
32  * Is used to specify the map key for associations of type
33  * {@link java.util.Map}.
34  *
35  * <p> If a persistent field or property other than the primary
36  * key is used as a map key then it is expected to have a
37  * uniqueness constraint associated with it.
38  *
39  * <pre>
40  *
41  * Example 1:
42  *
43  * &#064;Entity
44  * public class Department {
45  * ...
46  * &#064;OneToMany(mappedBy="department")
47  * &#064;MapKey(name="empId")
48  * public Map<Integer, Employee> getEmployees() {... }
49  * ...
50  * }
51  *
52  * &#064;Entity
53  * public class Employee {
54  * ...
55  * &#064;Id Integer getEmpid() { ... }
56  * &#064;ManyToOne
57  * &#064;JoinColumn(name="dept_id")
58  * public Department getDepartment() { ... }
59  * ...
60  * }
61  *
62  * Example 2:
63  *
64  * &#064;Entity
65  * public class Department {
66  * ...
67  * &#064;OneToMany(mappedBy="department")
68  * &#064;MapKey(name="empPK")
69  * public Map<EmployeePK, Employee> getEmployees() {... }
70  * ...
71  * }
72  *
73  * &#064;Entity
74  * public class Employee {
75  * &#064;EmbeddedId public EmployeePK getEmpPK() { ... }
76  * ...
77  * &#064;ManyToOne
78  * &#064;JoinColumn(name="dept_id")
79  * public Department getDepartment() { ... }
80  * ...
81  * }
82  *
83  * &#064;Embeddable
84  * public class EmployeePK {
85  * String name;
86  * Date bday;
87  * }
88  * </pre>
89  *
90  * @since Java Persistence 1.0
91  */

92 @Target JavaDoc({METHOD, FIELD})
93 @Retention JavaDoc(RUNTIME)
94
95 public @interface MapKey {
96
97     /**
98      * The name of the persistent field or property of the
99      * associated entity that is used as the map key. If the
100      * name element is not specified, the primary key of the
101      * associated entity is used as the map key. If the
102      * primary key is a composite primary key and is mapped
103      * as {@link IdClass}, an instance of the primary key
104      * class is used as the key.
105      */

106     String JavaDoc name() default "";
107 }
108
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