jakarta.persistence.MapKeyColumn Maven / Gradle / Ivy
/*
* 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
}