Package javax.persistence
Annotation Type MapKeyClass
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@Target({METHOD,FIELD}) @Retention(RUNTIME) public @interface MapKeyClass
Specifies the type of the map key for associations of typejava.util.Map
. The map key can be a basic type, an embeddable class, or an entity. If the map is specified using Java generics, theMapKeyClass
annotation and associated type need not be specified; otherwise they must be specified.The
MapKeyClass
annotation is used in conjunction withElementCollection
or one of the collection-valued relationship annotations (OneToMany
orManyToMany
). TheMapKey
annotation is not used whenMapKeyClass
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<String, String> 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<Division, VicePresident> organization; }
- Since:
- 2.0
- See Also:
ElementCollection
,OneToMany
,ManyToMany
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Required Element Summary
Required Elements Modifier and Type Required Element Description java.lang.Class
value
(Required) The type of the map key.
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