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/*
 * Copyright (c) 2008, 2024 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.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * Specifies the mapping for the key column of a map whose map key
 * is a basic type. If the {@link #name} element is not specified,
 * it defaults to the concatenation of the following: the name of
 * the referencing relationship field or property; "{@code _}";
 * "{@code KEY}".
 *
 * 

Example: * {@snippet : * @Entity * public class Item { * @Id * int id; * ... * @ElementCollection * @MapKeyColumn(name = "IMAGE_NAME") * @Column(name = "IMAGE_FILENAME") * @CollectionTable(name = "IMAGE_MAPPING") * Map images; // map from image name to filename * ... * } * } * @since 2.0 */ @Target( { METHOD, FIELD }) @Retention(RUNTIME) public @interface MapKeyColumn { /** * (Optional) The name of the map key column. The table in which * it is found depends upon the context. *

    *
  • If the map key is for an element collection, the map key * column is in the collection table for the map value. *
  • If the map key is for a {@link ManyToMany} entity * relationship or for a {@link OneToMany} entity relationship * using a join table, the map key column is in a join table. *
  • If the map key is for a {@code OneToMany} entity relationship * using a foreign key mapping strategy, the map key column is * in the table of the entity that is the value of the map. *
*

Defaults to the concatenation of the following: the name of * the referencing relationship field or property; "{@code _}"; * "{@code KEY}". */ String name() default ""; /** * (Optional) Whether the column is a unique key. This is a * shortcut for the {@link UniqueConstraint} annotation at the * table level and is useful for when the unique key constraint * corresponds to only a single column. This constraint applies * in addition to any constraint entailed by primary key mapping * and to constraints specified at the table level. */ boolean unique() default false; /** * (Optional) Whether the database column is nullable. */ boolean nullable() default false; /** * (Optional) Whether the column is included in SQL INSERT * statements generated by the persistence provider. */ boolean insertable() default true; /** * (Optional) Whether the column is included in SQL UPDATE * statements generated by the persistence provider. */ boolean updatable() default true; /** * (Optional) The SQL fragment that is used when generating * the DDL for the column. *

Defaults to the generated SQL to create a column of * the inferred 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 name of the table that contains the column. *

Defaults: If the map key is for an element collection, * the name of the collection table for the map value. If the * map key is for a {@link OneToMany} or {@link ManyToMany} * entity relationship using a join table, the name of the * join table for the map. If the map key is for a * {@link OneToMany} entity relationship using a foreign key * mapping strategy, the name of the primary table of the entity * that is the value of the map. */ String table() default ""; /** * (Optional) The column length. *

* Applies only to columns whose type is parameterized by length, * for example, {@code varchar} or {@code varbinary} types. */ int length() default 255; /** * (Optional) The precision for a column of SQL type {@code decimal} * or {@code numeric}, or of similar database-native type. *

* Applies only to columns of exact numeric type. *

* The default value {@code 0} indicates that a provider-determined * precision should be inferred. */ int precision() default 0; // decimal precision /** * (Optional) The scale for a column of SQL type {@code decimal} or * {@code numeric}, or of similar database-native type. *

* Applies only to columns of exact numeric type. *

* The default value {@code 0} indicates that a provider-determined * precision should be inferred. */ int scale() default 0; // decimal scale }





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