JPA Annotation

JoinColumn

Target: METHOD, FIELD
Implemented Interfaces:
Annotation
Specifies a column for joining an entity association or element collection. If the JoinColumn annotation itself is defaulted, a single join column is assumed and the default values apply.

Example:

 {@snippet :
See Also:
ManyToOne
OneToMany
OneToOne
JoinTable
CollectionTable
ForeignKey
Since:
JPA 1.0

Public Annotation Attributes

CheckConstraint[] check default {}
(Optional) Check constraints to be applied to the column.
These are only used if table generation is in effect.
Since:
JPA 3.2
String columnDefinition default ""
(Optional) The SQL fragment that is used when generating the DDL for the column.

Defaults to the generated SQL for the column.

Since:
JPA 1.0
String comment default ""
(Optional) A comment to be applied to the column.
This is only used if table generation is in effect.
Since:
JPA 3.2
ForeignKey foreignKey default @ForeignKey(PROVIDER_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:
JPA 2.1
boolean insertable default true
(Optional) Whether the column is included in SQL INSERT statements generated by the persistence provider.
Since:
JPA 1.0
String name default ""
(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 or ManyToOne 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 a OneToOne or bidirectional ManyToOne/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.

Since:
JPA 1.0
boolean nullable default true
(Optional) Whether the foreign key column is nullable.
Since:
JPA 1.0
String options default ""
(Optional) A SQL fragment appended to the generated DDL which declares this column.
May not be used in conjunction with JoinColumn.columnDefinition.
Since:
JPA 3.2
String referencedColumnName default ""
(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.

Since:
JPA 1.0
String table default ""
(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 or ManyToOne 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 a OneToOne or bidirectional ManyToOne/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.
Since:
JPA 1.0
boolean unique default false
(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. 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.
Since:
JPA 1.0
boolean updatable default true
(Optional) Whether the column is included in SQL UPDATE statements generated by the persistence provider.
Since:
JPA 1.0