javax.persistence.MapKeyColumn Maven / Gradle / Ivy
Show all versions of jakarta.persistence-api Show documentation
/*
* Copyright (c) 2008, 2019 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 javax.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 name element is not specified, it
* defaults to the concatenation of the following: the name of the
* referencing relationship field or property; "_"; "KEY".
*
*
* Example:
*
* @Entity
* public class Item {
* @Id int id;
* ...
* @ElementCollection
* @MapKeyColumn(name="IMAGE_NAME")
* @Column(name="IMAGE_FILENAME")
* @CollectionTable(name="IMAGE_MAPPING")
* Map<String, String> 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 ManyToMany entity relationship or for a OneToMany entity
* relationship using a join table, the map key column is in a join table.
* If the map key is for a 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; "_"; "KEY".
*/
String name() default "";
/**
* (Optional) Whether the column is a unique key. This is a
* shortcut for the 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) 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 OneToMany or ManyToMany entity
* relationship using a join table, the name of the join table
* for the map. If the map key is for a 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 if a string-valued column is
* used.)
*/
int length() default 255;
/**
* (Optional) The precision for a decimal (exact numeric) column. (Applies
* only if a decimal column is used.)
*
*
Default: 0. (The value must be set by the developer.)
*/
int precision() default 0; // decimal precision
/**
* (Optional) The scale for a decimal (exact numeric) column. (Applies only
* if a decimal column is used.)
*/
int scale() default 0; // decimal scale
}