src/javax/persistence/MapKeyColumn.java

/*******************************************************************************
 * Copyright (c) 1998, 2009 Oracle. 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:
 *     dclarke - Java Persistence 2.0 - Proposed Final Draft (March 13, 2009)
 *               Specification available from http://jcp.org/en/jsr/detail?id=317
 *
 * Java(TM) Persistence API, Version 2.0 - EARLY ACCESS
 * This is an implementation of an early-draft specification developed under the 
 * Java Community Process (JCP).  The code is untested and presumed not to be a  
 * compatible implementation of JSR 317: Java(TM) Persistence API, Version 2.0.   
 * We encourage you to migrate to an implementation of the Java(TM) Persistence 
 * API, Version 2.0 Specification that has been tested and verified to be compatible 
 * as soon as such an implementation is available, and we encourage you to retain 
 * this notice in any implementation of Java(TM) Persistence API, Version 2.0 
 * Specification that you distribute.
 ******************************************************************************/
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;

/**
 * The MapKeyColumn annotation is used to specify 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".
 * 
 * @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.
	 */
	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.
	 */
	String columnDefinition() default "";

	/** (Optional) The name of the table that contains the column. */
	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.)
	 */
	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
}