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package javax.persistence;
import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import static javax.persistence.DiscriminatorType.STRING;
/**
* Is used to define the discriminator column for the
* {@link InheritanceType#SINGLE_TABLE SINGLE_TABLE} and
* {@link InheritanceType#JOINED JOINED} inheritance mapping strategies.
*
* The 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
*
*
If the DiscriminatorColumn annotation is missing,
* and a discriminator column is required, the name of the
* discriminator column defaults to "DTYPE" and the discriminator
* type to {@link DiscriminatorType#STRING DiscriminatorType.STRING}.
*
*
* Example:
* @Entity
* @Table(name="CUST")
* @Inheritance(strategy=SINGLE_TABLE)
* @DiscriminatorColumn(name="DISC", discriminatorType=STRING,length=20)
* public class Customer { ... }
*
* @Entity
* public class ValuedCustomer extends Customer { ... }
*
*
* @since Java Persistence 1.0
*/
@Target({TYPE})
@Retention(RUNTIME)
public @interface DiscriminatorColumn {
/**
* (Optional) The name of column to be used for the discriminator.
*/
String name() default "DTYPE";
/**
* (Optional) The type of object/column to use as a class discriminator.
* Defaults to {@link DiscriminatorType#STRING DiscriminatorType.STRING}.
*/
DiscriminatorType discriminatorType() default STRING;
/**
* (Optional) The SQL fragment that is used when generating the DDL
* for the discriminator column.
* Defaults to the provider-generated SQL to create a column
* of the specified discriminator type.
*/
String columnDefinition() default "";
/**
* (Optional) The column length for String-based discriminator types.
* Ignored for other discriminator types.
*/
int length() default 31;
}