Menu
Is it possible to use an enum as a discriminator value when using SINGLE_TABLE inheritance strategy?
798
The discriminator column is always in the table of the base entity. It holds a different value for records of each class, allowing the JPA runtime to determine what class of object each row represents. The DiscriminatorColumn annotation represents a discriminator column.
In case of table per class hierarchy an discriminator column is added by the hibernate framework that specifies the type of the record. It is mainly used to distinguish the record. To specify this, discriminator subelement of class must be specified. The subclass subelement of class, specifies the subclass.
There are three inheritance mapping strategies defined in the hibernate: Table Per Hierarchy. Table Per Concrete class. Table Per Subclass.
javax.persistence @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 what you are trying to achieve is to not to duplicate the discriminator values, there is a simple workaround.
@Entity @Inheritance(strategy=InheritanceType.SINGLE_TABLE) @DiscriminatorColumn(name="FREQUENCY", discriminatorType=DiscriminatorType.STRING ) public abstract class Event { } @Entity @DiscriminatorValue(value=Frequency.Values.WEEKLY) public class WeeklyEvent extends Event { … } public enum Frequency { DAILY(Values.DAILY), WEEKLY(Values.WEEKLY), MONTHLY(Values.MONTHLY); private String value; … public static class Values { public static final String DAILY = "D"; public static final String WEEKLY = "W"; public static final String MONTHLY = "M"; } } Nothing to do with Hibernate/JPA really, but better than having to maintain the values in multiple places.
126
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
