程序包 org.hibernate.annotations

注释类型 Any

@Target({METHOD,FIELD})
@Retention(RUNTIME)
public @interface Any

Defines a ToOne-style association pointing to one of several entity types depending on a local discriminator, as opposed to discriminated inheritance where the discriminator is kept as part of the entity hierarchy. For example, if you consider an Order entity containing Payment information where Payment might be of type CashPayment or CreditCardPayment the @Any approach would be to keep that discriminator and matching value on the Order itself. Thought of another way, the "foreign-key" really is made up of the value and discriminator (there is no physical foreign key here as databases do not support this):

    @Entity
    class Order {
        ...
        @Any( metaColumn = @Column( name="payment_type" ) )
        @AnyMetDef(
                idType = "long"
                metaValues = {
                        @MetaValue( value="C", targetEntity=CashPayment.class ),
                        @MetaValue( value="CC", targetEntity=CreditCardPayment.class ),
                }
        )
        pubic Payment getPayment() { ... }
    }
 }
 

作者:

Emmanuel Bernard, Steve Ebersole

另请参阅:

AnyMetaDef

必需元素概要

所需元素

修饰符和类型	必需的元素	说明
javax.persistence.Column	metaColumn	Identifies the discriminator column.

可选元素概要

可选元素

修饰符和类型	可选元素	说明
javax.persistence.FetchType	fetch	Defines whether the value of the field or property should be lazily loaded or must be eagerly fetched.
String	metaDef	Metadata definition used.
boolean	optional	Whether the association is optional.

元素详细资料

metaColumn

javax.persistence.Column metaColumn

Identifies the discriminator column. This column will hold the value that identifies the targeted entity.

metaDef

String metaDef

Metadata definition used. If defined, should point to a @AnyMetaDef name If not defined, the local (ie in the same field or property) @AnyMetaDef is used

默认值:

""

fetch

javax.persistence.FetchType fetch

Defines whether the value of the field or property should be lazily loaded or must be eagerly fetched. The EAGER strategy is a requirement on the persistence provider runtime that the value must be eagerly fetched. The LAZY strategy is applied when bytecode enhancement is used. If not specified, defaults to EAGER.

默认值:

javax.persistence.FetchType.EAGER

optional

boolean optional

Whether the association is optional. If set to false then a non-null relationship must always exist.

默认值:

true