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@Target(value={METHOD,FIELD}) @Retention(value=RUNTIME) public @interface MapKeyJoinColumn
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 noMapKeyJoinColumn
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
- See Also:
ForeignKey
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Optional Element Summary
Optional Elements Modifier and Type Optional Element and Description String
columnDefinition
(Optional) The SQL fragment that is used when generating the DDL for the column.ForeignKey
foreignKey
(Optional) Used to specify or control the generation of a foreign key constraint when table generation is in effect.boolean
insertable
(Optional) Whether the column is included in SQL INSERT statements generated by the persistence provider.String
name
(Optional) The name of the foreign key column for the map key.boolean
nullable
(Optional) Whether the foreign key column is nullable.String
referencedColumnName
(Optional) The name of the column referenced by this foreign key column.String
table
(Optional) The name of the table that contains the foreign key column.boolean
unique
(Optional) Whether the property is a unique key.boolean
updatable
(Optional) Whether the column is included in SQL UPDATE statements generated by the persistence provider.
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Element Detail
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name
public abstract String name
(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".
- Default:
- ""
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referencedColumnName
public abstract String referencedColumnName
(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
- Default:
- ""
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unique
public abstract boolean unique
(Optional) Whether the property is a unique key. This is a shortcut for theUniqueConstraint
annotation at the table level and is useful for when the unique key constraint is only a single field.- Default:
- false
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nullable
public abstract boolean nullable
(Optional) Whether the foreign key column is nullable.- Default:
- false
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insertable
public abstract boolean insertable
(Optional) Whether the column is included in SQL INSERT statements generated by the persistence provider.- Default:
- true
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updatable
public abstract boolean updatable
(Optional) Whether the column is included in SQL UPDATE statements generated by the persistence provider.- Default:
- true
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columnDefinition
public abstract String columnDefinition
(Optional) The SQL fragment that is used when generating the DDL for the column. Defaults to SQL generated by the provider for the column.- Default:
- ""
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table
public abstract String table
(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.
- Default:
- ""
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foreignKey
public abstract ForeignKey foreignKey
(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
- Default:
- @javax.persistence.ForeignKey(javax.persistence.ConstraintMode.PROVIDER_DEFAULT)
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Nederlandse vertaling
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Bij voorbaat dank.
Document heeft de 11/06/2005 gemaakt, de laatste keer de 18/08/2025 gewijzigd
Bron van het afgedrukte document:https://www.gaudry.be/nl/java-api-javaee-rf-javax/persistence/MapKeyJoinColumn.html
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