DiscriminatorValue (Java EE 5 SDK)

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Java EE 5 SDK

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摘要: REQUIRED | OPTIONAL

详细信息: ELEMENT

javax.persistence Annotation Type DiscriminatorValue

@Target(value=TYPE) @Retention(value=RUNTIME) public @interface DiscriminatorValue

Is used to specify the value of the discriminator column for entities of the given type. The DiscriminatorValue annotation can only be specified on a concrete entity class. If the DiscriminatorValue annotation is not specified and a discriminator column is used, a provider-specific function will be used to generate a value representing the entity type. If the DiscriminatorType is STRING, the discriminator value default is the entity name.

The inheritance strategy and the discriminator column are only specified in the root of an entity class hierarchy or subhierarchy in which a different inheritance strategy is applied. The discriminator value, if not defaulted, should be specified for each entity class in the hierarchy.


    Example:

    @Entity
    @Table(name="CUST")
    @Inheritance(strategy=SINGLE_TABLE)
    @DiscriminatorColumn(name="DISC", discriminatorType=STRING,length=20)
    @DiscriminatorValue("CUSTOMER")
    public class Customer { ... }

    @Entity
    @DiscriminatorValue("VCUSTOMER")
    public class ValuedCustomer extends Customer { ... }

从以下版本开始:: Java Persistence 1.0

Required Element Summary
`String`	`value` (Optional) The value that indicates that the row is an entity of the annotated entity type.

元素详细信息

value

public abstract String value

(Optional) The value that indicates that the row is an entity of the annotated entity type.

If the DiscriminatorValue annotation is not specified and a discriminator column is used, a provider-specific function will be used to generate a value representing the entity type. If the DiscriminatorType is STRING, the discriminator value default is the entity name.

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