jakarta.persistence.DiscriminatorColumn Maven / Gradle / Ivy
/*
* Copyright (c) 2008, 2023 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0,
* or the Eclipse Distribution License v. 1.0 which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
*/
// Contributors:
// Linda DeMichiel - 2.1
// Linda DeMichiel - 2.0
package jakarta.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 jakarta.persistence.DiscriminatorType.STRING;
/**
* Specifies the discriminator column for the
* {@link InheritanceType#SINGLE_TABLE SINGLE_TABLE} and
* {@link InheritanceType#JOINED JOINED} {@linkplain Inheritance
* inheritance mapping strategies}.
*
* The mapping strategy and discriminator column are only specified
* for the root of an entity class hierarchy or subhierarchy in which
* a different inheritance strategy is applied.
*
*
If the {@link DiscriminatorColumn} annotation is missing, and a
* discriminator column is required, the name of the discriminator
* column defaults to {@code "DTYPE"} and the discriminator type to
* {@link DiscriminatorType#STRING}.
*
*
Example:
* {@snippet :
* @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
* @see DiscriminatorType
*
* @since 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) A SQL fragment appended to the generated DDL
* which declares this column. May not be used in
* conjunction with {@link #columnDefinition()}.
*
* @since 3.2
*/
String options() default "";
/**
* (Optional) The column length for String-based discriminator types.
* Ignored for other discriminator types.
*/
int length() default 31;
}