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@Repeatable(JoinColumns.class) @Target({METHOD,FIELD}) @Retention(RUNTIME) public @interface JoinColumn
Specifies a column for joining an entity association or element collection. If theJoinColumn
annotation itself is defaulted, a single join column is assumed and the default values apply.Example: {@snippet :
- Since:
- 1.0
- See Also:
ManyToOne
,OneToMany
,OneToOne
,JoinTable
,CollectionTable
,ForeignKey
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Optional Element Summary
Optional Elements Modifier and Type Optional Element Description CheckConstraint[]
check
(Optional) Check constraints to be applied to the column.java.lang.String
columnDefinition
(Optional) The SQL fragment that is used when generating the DDL for the column.java.lang.String
comment
(Optional) A comment to be applied to 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.java.lang.String
name
(Optional) The name of the foreign key column.boolean
nullable
(Optional) Whether the foreign key column is nullable.java.lang.String
options
(Optional) A SQL fragment appended to the generated DDL which declares this column.java.lang.String
referencedColumnName
(Optional) The name of the column referenced by this foreign key column.java.lang.String
table
(Optional) The name of the table that contains the 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
java.lang.String name
(Optional) The name of the foreign key column.The table in which this column is found depends on the context.
- If the join is for a
OneToOne
orManyToOne
mapping using a foreign key mapping strategy, the foreign key column is in the table of the source entity or embeddable. - If the join is for a unidirectional
OneToMany
mapping using a foreign key mapping strategy, the foreign key is in the table of the target entity. - If the join is for a
ManyToMany
mapping or for aOneToOne
or bidirectionalManyToOne
/OneToMany
mapping using a join table, the foreign key is in a join table. - If the join is for an
ElementCollection
, the foreign key is in a collection table.
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; "
_
"; the name of the referenced primary key column. If there is no such referencing relationship property or field in the entity, or if the join is for an element collection, the join column name is formed as the concatenation of the following: the name of the entity; "_
"; the name of the referenced primary key column.- Default:
- ""
- If the join is for a
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referencedColumnName
java.lang.String referencedColumnName
(Optional) The name of the column referenced by this foreign key column.- When used with entity relationship mappings other than the cases described here, the referenced column is in the table of the target entity.
- When used with a unidirectional
OneToMany
foreign key mapping, the referenced column is in the table of the source entity. - When used inside a
JoinTable
annotation, the referenced key column is in the entity table of the owning entity, or inverse entity if the join is part of the inverse join definition. - When used in a
CollectionTable
mapping, the referenced column is in the table of the entity containing the collection.
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
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. It is not necessary to explicitly specify this for a join column that corresponds to a primary key that is part of a foreign key.- Default:
- false
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options
java.lang.String options
(Optional) A SQL fragment appended to the generated DDL which declares this column. May not be used in conjunction withcolumnDefinition()
.- Since:
- 3.2
- Default:
- ""
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table
java.lang.String table
(Optional) The name of the table that contains the column. If a table is not specified, the column is assumed to be in the primary table of the applicable entity.Default:
- If the join is for a
OneToOne
orManyToOne
mapping using a foreign key mapping strategy, the name of the table of the source entity or embeddable. - If the join is for a unidirectional OneToMany mapping using a foreign key mapping strategy, the name of the table of the target entity.
- If the join is for a
ManyToMany
mapping or for aOneToOne
or bidirectionalManyToOne
/OneToMany
mapping using a join table, the name of the join table. - If the join is for an element collection, the name of the collection table.
- Default:
- ""
- If the join is for a
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foreignKey
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, a default foreign key strategy is selected by the persistence provider.- Since:
- 2.1
- Default:
- @jakarta.persistence.ForeignKey(jakarta.persistence.ConstraintMode.PROVIDER_DEFAULT)
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check
CheckConstraint[] check
(Optional) Check constraints to be applied to the column. These are only used if table generation is in effect.- Since:
- 3.2
- Default:
- {}
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