javax.persistence.MapKeyJoinColumn Maven / Gradle / Ivy
Show all versions of jakarta.persistence-api Show documentation
/*
* Copyright (c) 2008, 2019 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:
// Petros Splinakis - 2.2
// Linda DeMichiel - 2.1
// Linda DeMichiel - 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 ForeignKey
*
* @since 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".
*/
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
*/
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.
*/
boolean unique() default false;
/**
* (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.
*/
boolean insertable() default true;
/**
* (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.
*/
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.
*
*/
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 2.1
*/
ForeignKey foreignKey() default @ForeignKey(PROVIDER_DEFAULT);
}