javax.persistence.MapKeyColumn.java Source code

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Here is the source code for javax.persistence.MapKeyColumn.java

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/*******************************************************************************
 * Copyright (c) 2008 - 2013 Oracle Corporation. 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.
 *
 * Contributors:
 *     Linda DeMichiel - Java Persistence 2.1
 *     Linda DeMichiel - Java Persistence 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 <code>name</code> element is not specified, it
 * defaults to the concatenation of the following: the name of the
 * referencing relationship field or property; "_"; "KEY".
 * 
 * <pre>
 *    Example:
 *
 *    &#064;Entity
 *    public class Item {
 *       &#064;Id int id;
 *       ...
 *       &#064;ElementCollection
 *       &#064;MapKeyColumn(name="IMAGE_NAME")
 *       &#064;Column(name="IMAGE_FILENAME")
 *       &#064;CollectionTable(name="IMAGE_MAPPING")
 *       Map&#060;String, String&#062; images;  // map from image name to filename
 *       ...
 *    } 
 * </pre>
 * @since Java Persistence 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.
     * <p> Defaults to the concatenation of the following: the name of
     * the referencing relationship field or property; "_"; "<code>KEY</code>".
     */
    String name() default "";

    /**
     * (Optional) Whether the column is a unique key. This is a
     * shortcut for the <code>UniqueConstraint</code> 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.
     * <p> 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. 
     *
     * <p> 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.)  
     *
     *<p> 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
}