MapKeyJoinColumn
Target: METHOD, FIELD
- Implemented Interfaces:
Annotation
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; ... }
- See Also:
ForeignKey
- Since:
- JPA 2.0
Public Annotation Attributes
String columnDefinition default ""
Defaults to SQL generated by the provider for the column.
- Since:
- JPA 2.0
If this element is not specified, the persistence provider's default foreign key strategy will apply.
- Since:
- JPA 2.1
boolean insertable default true
- Since:
- JPA 2.0
String name default ""
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".
- Since:
- JPA 2.0
boolean nullable default false
- Since:
- JPA 2.0
String referencedColumnName default ""
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
- Since:
- JPA 2.0
String table default ""
- 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.
- Since:
- JPA 2.0
boolean unique default false
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. - Since:
- JPA 2.0
boolean updatable default true
- Since:
- JPA 2.0