javax.persistence.MapKeyClass - JPA annotation
javax.persistence
Annotation MapKeyClass
- Target:
- Fields (including property get methods)
java.util.Map
. The map key can be a basic type, an embeddable class, or an entity. If the map is specified using Java generics, the MapKeyClass
annotation and associated type need not be specified; otherwise they must be specified. The MapKeyClass
annotation is used in conjunction with ElementCollection
or one of the collection-valued relationship annotations (OneToMany
or ManyToMany
). The MapKey
annotation is not used when MapKeyClass
is specified and vice versa.
Example 1:
@Entity public class Item { @Id int id; ... @ElementCollection(targetClass=String.class) @MapKeyClass(String.class) Map images; // map from image name to image filename ... }
Example 2:
// MapKeyClass and target type of relationship can be defaulted @Entity public class Item { @Id int id; ... @ElementCollection Map images; ... }
Example 3:
@Entity public class Company { @Id int id; ... @OneToMany(targetEntity=com.example.VicePresident.class) @MapKeyClass(com.example.Division.class) Map organization; }
Example 4:
// MapKeyClass and target type of relationship are defaulted @Entity public class Company { @Id int id; ... @OneToMany Map organization; }
- Since:
- JPA 2.0
- See Also:
-
ElementCollection
-
OneToMany
-
ManyToMany
- Since:
- JPA 2.0