javax.persistence.MapKeyColumn Maven / Gradle / Ivy
/*
* Copyright (c) 2008, 2009, 2011 Oracle, Inc. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
* which accompanies this distribution. The Eclipse Public License is available
* at http://www.eclipse.org/legal/epl-v10.html and the Eclipse Distribution License
* is available at http://www.eclipse.org/org/documents/edl-v10.php.
*/
package javax.persistence;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.FIELD;
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 Java Persistence 2.0
*/
@Target({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".
*
* @return The name
*/
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.
*
* @return Whether unique
*/
boolean unique() default false;
/**
* (Optional) Whether the database column is nullable.
*
* @return Whether nullable
*/
boolean nullable() default false;
/**
* (Optional) Whether the column is included in SQL INSERT statements generated by the persistence
* provider.
*
* @return Whether insertable
*/
boolean insertable() default true;
/**
* (Optional) Whether the column is included in SQL UPDATE statements generated by the persistence
* provider.
*
* @return Whether updateable
*/
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.
*
* @return The column definition
*/
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.
*
* @return The table
*/
String table() default "";
/**
* (Optional) The column length. (Applies only if a string-valued column is used.)
*
* @return The length
*/
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.)
*
* @return The precision
*/
int precision() default 0; // decimal precision
/**
* (Optional) The scale for a decimal (exact numeric) column. (Applies only if a decimal column is used.)
*
* @return The scale
*/
int scale() default 0; // decimal scale
}