MapKeyClass (Jakarta Persistence API documentation)

```
@Target({METHOD,FIELD})
@Retention(RUNTIME)
public @interface MapKeyClass
```
Specifies the type of the map key for associations of type 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: {@snippet :

Since:

2.0

See Also:

ElementCollection, OneToMany, ManyToMany

- Required Element Summary
  
  Required Elements
  Modifier and Type Required Element Description
  
  Class<?> value
  (Required) The type of the map key.

- Element Detail
  - value
```
Class<?> value
```
    (Required) The type of the map key.