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@Target(value={METHOD,FIELD})
@Retention(value=RUNTIME)
public @interface MapKey
Is used to specify the map key for associations of type
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;
}
| Optional Element Summary | |
|---|---|
String |
name
The name of the persistent field or property of the associated entity that is used as the map key. |
public abstract String name
IdClass, an instance of the primary key
class is used as the key.
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Copyright 2006 Sun Microsystems, Inc. All rights reserved.