Maps a to-one cardinality association taking values over several entity types which are not related by the usual entity inheritance, using a discriminator value stored on the referring side of the relationship.

This is quite different to discriminated inheritance where the discriminator is stored along with the referenced entity hierarchy.

For example, consider an Order entity containing Payment information, where a Payment might be a CashPayment or a CreditCardPayment. An @Any mapping would store the discriminator value identifying the concrete type of Payment along with the state of the associated Order, instead of storing it with the Payment entity itself.

interface Payment { ... }

@Entity
class CashPayment { ... }

@Entity
class CreditCardPayment { ... }

@Entity
class Order {
    ...
    @Any
    @AnyKeyJavaClass(UUID.class)   //the foreign key type
    @JoinColumn(name="payment_id") //the foreign key column
    @Column(name="payment_type")   //the discriminator column
    @AnyDiscriminatorValue(discriminator="CASH", entity=CashPayment.class)
    @AnyDiscriminatorValue(discriminator="CREDIT", entity=CreditCardPayment.class)
    Payment payment;
    ...
}

In this example, Payment is not be declared as an entity type, and is not annotated @Entity. It might even be an interface, or at most just a mapped superclass, of CashPayment and CreditCardPayment. So in terms of the object/relational mappings, CashPayment and CreditCardPayment would not be considered to participate in the same entity inheritance hierarchy. On the other hand, CashPayment and CreditCardPayment must have the same identifier type.

It's reasonable to think of the "foreign key" in an Any mapping is really a composite value made up of the foreign key and discriminator taken together. Note, however, that this composite foreign key is only conceptual and cannot be declared as a physical constraint on the relational database table.

• AnyDiscriminator, JdbcType, or JdbcTypeCode specifies the type of the discriminator.
• AnyDiscriminatorValue specifies how discriminator values map to entity types.
• jakarta.persistence.Column or Formula specifies the column or formula in which the discriminator value is stored.
• AnyKeyJavaType, AnyKeyJavaClass, AnyKeyJdbcType, or AnyKeyJdbcTypeCode specifies the type of the foreign key.
• jakarta.persistence.JoinColumn specifies the foreign key column.

Of course, Any mappings are disfavored, except in extremely special cases, since it's much more difficult to enforce referential integrity at the database level.