Package javax.persistence
Annotation Type MapKey
-
@Target({METHOD,FIELD}) @Retention(RUNTIME) public @interface MapKeySpecifies the map key for associations of typejava.util.Mapwhen the map key is itself the primary key or a persistent field or property of the entity that is the value of the 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.
The
MapKeyClassannotation is not used whenMapKeyis specified and vice versa.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() { ... } ... }- Since:
- 1.0
-
-
Optional Element Summary
Optional Elements Modifier and Type Optional Element Description java.lang.Stringname(Optional) The name of the persistent field or property of the associated entity that is used as the map key.
-
-
-
Element Detail
-
name
java.lang.String name
(Optional) The name of the persistent field or property of the associated entity that is used as the map key.Default: If the
nameelement 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 asIdClass, an instance of the primary key class is used as the key.- Default:
- ""
-
-