javax.persistence.MapKeyJoinColumn Maven / Gradle / Ivy
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/*
* Copyright (c) 2008, 2009, 2011 Oracle, Inc. 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.
*/
package javax.persistence;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Repeatable;
/**
* 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;
* ...
* }
*
* @since Java Persistence 2.0
*/
@Target({ANNOTATION_TYPE, METHOD, FIELD})
@Retention(RUNTIME)
@Repeatable(MapKeyJoinColumns.class)
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".
* @return The name
*/
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
* @return The referenced col name
*/
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.
* @return Whether unique
*/
boolean unique() default false;
/**
* (Optional) Whether the foreign key column is nullable.
* @return Whether nullable
*/
boolean nullable() default false;
/**
* (Optional) Whether the column is included in SQL INSERT statements generated by the persistence
* provider.
* @return Whether insertable
*/
boolean insertable() default true;
/**
* (Optional) Whether the column is included in SQL UPDATE statements generated by the persistence
* provider.
* @return Whether updateable
*/
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.
* @return The column definition
*/
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.
*
* @return The table
*/
String table() default "";
/**
* (Optional) The foreign key constraint specification for the join column. This is used only if table
* generation is in effect. Default is provider defined.
* @return The foreign key specification
*/
ForeignKey foreignKey() default @ForeignKey();
}