javax.persistence.DiscriminatorColumn Maven / Gradle / Ivy
package javax.persistence;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import static javax.persistence.DiscriminatorType.STRING;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
/**
* Specifies the discriminator column for the SINGLE_TABLE and JOINED {@link 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 { ... }
*
*
* @see DiscriminatorValue
*
* @since Java Persistence 1.0
*/
@Target({ TYPE })
@Retention(RUNTIME)
public @interface DiscriminatorColumn {
/**
* (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 type of object/column to use as a class discriminator. Defaults to {@link DiscriminatorType#STRING
* DiscriminatorType.STRING}.
*/
DiscriminatorType discriminatorType() default STRING;
/**
* (Optional) The column length for String-based discriminator types. Ignored for other discriminator types.
*/
int length() default 31;
/**
* (Optional) The name of column to be used for the discriminator.
*/
String name() default "DTYPE";
}