jakarta.persistence.MapKeyJoinColumn Maven / Gradle / Ivy
/*
* Copyright (c) 2008, 2023 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 jakarta.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;
/**
* 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}
* annotation is specified, a single join column is assumed and the default
* values apply.
*
* Example 1:
* {@snippet :
* @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 organization;
* }
* }
*
* Example 2:
* {@snippet :
* @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 videoInventory;
* ...
* }
*
* @Entity
* public class Movie {
* @Id long id;
* String title;
* ...
* }
* }
*
* Example 3:
* {@snippet :
* @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 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 {@link ManyToMany}
* entity relationship or for a {@link OneToMany} entity
* relationship using a join table, the foreign key column
* is in a join table.
*
- If the join is for a {@link 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; "{@code _}"; "{@code 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 {@link 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) A SQL fragment appended to the generated DDL
* which declares this column. May not be used in
* conjunction with {@link #columnDefinition()}.
*
* @since 3.2
*/
String options() 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 {@link ManyToMany}
* entity relationship or for a {@link OneToMany} entity
* relationship using a join table, the foreign key column
* is in a join table.
*
- If the join is for a {@link 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 {@link OneToMany} or {@link ManyToMany}
* entity relationship using a join table, the name of the join
* table for the map.
*
- If the map is for a {@link 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, a default foreign key
* strategy is selected by the persistence provider.
*
* @since 2.1
*/
ForeignKey foreignKey() default @ForeignKey(ConstraintMode.PROVIDER_DEFAULT);
}