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//$Id: DiscriminatorColumn.java 11282 2007-03-14 22:05:59Z epbernard $

//EJB3 Specification Copyright 2004-2006 Sun Microsystems, Inc.

package javax.persistence;

import java.lang.annotation.Retention;

import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.*;

import static java.lang.annotation.RetentionPolicy.*;

import static javax.persistence.DiscriminatorType.STRING;

/**

 * Is used to define the discriminator column for the SINGLE_TABLE and 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

 * DiscriminatorType.STRING.

 *

 * @author Emmanuel Bernard

 */

@Target({TYPE}) @Retention(RUNTIME)

public @interface DiscriminatorColumn {

        /**

         * The name of column to be used for the discriminator.

         */

        String name() default "DTYPE";

        /**

         * The type of object/column to use as a class discriminator.

         * Defaults to DiscriminatorType.STRING

         */

        DiscriminatorType discriminatorType() default STRING;

        /**

         * 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 "";

        /**

         * The column length for String-based discriminator types. Ignored for other

         * discriminator types.

         */

        int length() default 31;

}