javax.persistence.DiscriminatorColumn Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2008 - 2013 Oracle Corporation. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
* which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Linda DeMichiel - Java Persistence 2.1
* Linda DeMichiel - Java Persistence 2.0
*
******************************************************************************/
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;
/**
* 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 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;
}