Copyright (c) 2008 - 2015 Oracle Corporation. All rights reserved.
This program and the accompanying materials are made available under the
terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
which accompanies this distribution.
The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
and the Eclipse Distribution License is available at
http://www.eclipse.org/org/documents/edl-v10.php.
Contributors:
Petros Splinakis - Java Persistence 2.2
Linda DeMichiel - Java Persistence 2.1
Linda DeMichiel - Java Persistence 2.0
/*******************************************************************************
* Copyright (c) 2008 - 2015 Oracle Corporation. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
* which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Petros Splinakis - Java Persistence 2.2
* Linda DeMichiel - Java Persistence 2.1
* Linda DeMichiel - Java Persistence 2.0
*
******************************************************************************/
package javax.persistence;
import java.lang.annotation.Repeatable;
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;
import static javax.persistence.ConstraintMode.PROVIDER_DEFAULT;
Specifies a mapping to an entity that is a map key. The map key
join column is in the collection table, join table, or table of the
target entity that is used to represent the map. If no
MapKeyJoinColumn annotation is specified, a single
join column is assumed and the default values apply.
Example 1:
@Entity
public class Company {
@Id int id;
...
@OneToMany // unidirectional
@JoinTable(name="COMPANY_ORGANIZATION",
joinColumns=@JoinColumn(name="COMPANY"),
inverseJoinColumns=@JoinColumn(name="VICEPRESIDENT"))
@MapKeyJoinColumn(name="DIVISION")
Map<Division, VicePresident> organization;
}
Example 2:
@Entity
public class VideoStore {
@Id int id;
String name;
Address location;
...
@ElementCollection
@CollectionTable(name="INVENTORY",
joinColumns=@JoinColumn(name="STORE"))
@Column(name="COPIES_IN_STOCK")
@MapKeyJoinColumn(name="MOVIE", referencedColumnName="ID")
Map<Movie, Integer> videoInventory;
...
}
@Entity
public class Movie {
@Id long id;
String title;
...
}
Example 3:
@Entity
public class Student {
@Id int studentId;
...
@ManyToMany // students and courses are also many-many
@JoinTable(name="ENROLLMENTS",
joinColumns=@JoinColumn(name="STUDENT"),
inverseJoinColumns=@JoinColumn(name="SEMESTER"))
@MapKeyJoinColumn(name="COURSE")
Map<Course, Semester> enrollment;
...
}
See Also: - ForeignKey
Since: Java Persistence 2.0
/**
* Specifies a mapping to an entity that is a map key. The map key
* join column is in the collection table, join table, or table of the
* target entity that is used to represent the map. If no
* <code>MapKeyJoinColumn</code> annotation is specified, a single
* join column is assumed and the default values apply.
*
* <pre>
*
* Example 1:
*
* @Entity
* public class Company {
* @Id int id;
* ...
* @OneToMany // unidirectional
* @JoinTable(name="COMPANY_ORGANIZATION",
* joinColumns=@JoinColumn(name="COMPANY"),
* inverseJoinColumns=@JoinColumn(name="VICEPRESIDENT"))
* @MapKeyJoinColumn(name="DIVISION")
* Map<Division, VicePresident> organization;
* }
*
* Example 2:
*
* @Entity
* public class VideoStore {
* @Id int id;
* String name;
* Address location;
* ...
* @ElementCollection
* @CollectionTable(name="INVENTORY",
* joinColumns=@JoinColumn(name="STORE"))
* @Column(name="COPIES_IN_STOCK")
* @MapKeyJoinColumn(name="MOVIE", referencedColumnName="ID")
* Map<Movie, Integer> videoInventory;
* ...
* }
*
* @Entity
* public class Movie {
* @Id long id;
* String title;
* ...
* }
*
* Example 3:
*
* @Entity
* public class Student {
* @Id int studentId;
* ...
* @ManyToMany // students and courses are also many-many
* @JoinTable(name="ENROLLMENTS",
* joinColumns=@JoinColumn(name="STUDENT"),
* inverseJoinColumns=@JoinColumn(name="SEMESTER"))
* @MapKeyJoinColumn(name="COURSE")
* Map<Course, Semester> enrollment;
* ...
* }
* </pre>
*
* @see ForeignKey
*
* @since Java Persistence 2.0
*/
@Repeatable(MapKeyJoinColumns.class)
@Target( { METHOD, FIELD })
@Retention(RUNTIME)
public @interface MapKeyJoinColumn {
(Optional) The name of the foreign key column for the map
key. The table in which it is found depends upon the
context.
- If the join is for a map key for an
element collection, the foreign key column is in the
collection table for the map value.
- If the join is for a map key for a ManyToMany entity
relationship or for a OneToMany entity relationship
using a join table, the foreign key column is in a join table.
- If the join is for a OneToMany entity relationship using
a foreign key mapping strategy, the foreign key column for the
map key is in the table of the entity that is the value of the map.
Default (only applies if a single join column is used.)
The concatenation of the following: the name of the
referencing relationship property or field of the
referencing entity or embeddable class; "_"; "KEY".
/**
* (Optional) The name of the foreign key column for the map
* key. The table in which it is found depends upon the
* context.
* <ul>
* <li> If the join is for a map key for an
* element collection, the foreign key column is in the
* collection table for the map value.
* <li> If the join is for a map key for a ManyToMany entity
* relationship or for a OneToMany entity relationship
* using a join table, the foreign key column is in a join table.
* <li> If the join is for a OneToMany entity relationship using
* a foreign key mapping strategy, the foreign key column for the
* map key is in the table of the entity that is the value of the map.
* </ul>
*
* <p> Default (only applies if a single join column is used.)
* The concatenation of the following: the name of the
* referencing relationship property or field of the
* referencing entity or embeddable class; "_"; "KEY".
*/
String name() default "";
(Optional) The name of the column referenced by this foreign key column.
The referenced column is in the table of the target entity.
Default (only applies if single join column is being
used.) The same name as the primary key column of the
referenced table
/**
* (Optional) The name of the column referenced by this foreign key column.
* The referenced column is in the table of the target entity.
*
* <p> Default (only applies if single join column is being
* used.) The same name as the primary key column of the
* referenced table
*/
String referencedColumnName() default "";
(Optional) Whether the property is a unique key. This is a
shortcut for the UniqueConstraint annotation
at the table level and is useful for when the unique key
constraint is only a single field.
/**
* (Optional) Whether the property is a unique key. This is a
* shortcut for the <code>UniqueConstraint</code> annotation
* at the table level and is useful for when the unique key
* constraint is only a single field.
*/
boolean unique() default false;
(Optional) Whether the foreign key column is nullable.
/**
* (Optional) Whether the foreign key column is nullable.
*/
boolean nullable() default false;
(Optional) Whether the column is included in SQL INSERT statements
generated by the persistence provider.
/**
* (Optional) Whether the column is included in SQL INSERT statements
* generated by the persistence provider.
*/
boolean insertable() default true;
(Optional) Whether the column is included in SQL UPDATE statements
generated by the persistence provider.
/**
* (Optional) Whether the column is included in SQL UPDATE statements
* generated by the persistence provider.
*/
boolean updatable() default true;
(Optional) The SQL fragment that is used when generating the DDL for the
column.
Defaults to SQL generated by the provider for the column.
/**
* (Optional) The SQL fragment that is used when generating the DDL for the
* column.
* Defaults to SQL generated by the provider for the column.
*/
String columnDefinition() default "";
(Optional) The name of the table that contains the foreign key column.
- If the join is for a map key for an element collection, the foreign key
column is in the collection table for the map value.
- If the join is for a map key for a ManyToMany entity relationship
or for a OneToMany entity relationship using a join table,
the foreign key column is in a join table.
- If the join is for a OneToMany entity relationship using a foreign
key mapping strategy, the foreign key column for the map key is in the
table of the entity that is the value of the map.
Default:
- If the map is for an element collection, the
name of the collection table for the map value.
- If the map is for a OneToMany or ManyToMany entity relationship
using a join table, the name of the join table for the map.
- If the map is for a OneToMany entity relationship using a
foreign key mapping strategy, the name of the primary table
of the entity that is the value of the map.
/**
* (Optional) The name of the table that contains the foreign key column.
* <ul>
* <li> If the join is for a map key for an element collection, the foreign key
* column is in the collection table for the map value.
* <li> If the join is for a map key for a ManyToMany entity relationship
* or for a OneToMany entity relationship using a join table,
* the foreign key column is in a join table.
* <li> If the join is for a OneToMany entity relationship using a foreign
* key mapping strategy, the foreign key column for the map key is in the
* table of the entity that is the value of the map.
* </ul>
* <p> Default:
* <ul>
* <li> If the map is for an element collection, the
* name of the collection table for the map value.
* <li> If the map is for a OneToMany or ManyToMany entity relationship
* using a join table, the name of the join table for the map.
* <li> If the map is for a OneToMany entity relationship using a
* foreign key mapping strategy, the name of the primary table
* of the entity that is the value of the map.
* </ul>
*/
String table() default "";
(Optional) Used to specify or control the generation of a
foreign key constraint when table generation is in effect. If
this element is not specified, the persistence provider's
default foreign key strategy will apply.
@since Java Persistence 2.1
/**
* (Optional) Used to specify or control the generation of a
* foreign key constraint when table generation is in effect. If
* this element is not specified, the persistence provider's
* default foreign key strategy will apply.
*
* @since Java Persistence 2.1
*/
ForeignKey foreignKey() default @ForeignKey(PROVIDER_DEFAULT);
}