/*
* Copyright (c) 2008, 2009 Sun Microsystems. 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 2.0 - Version 2.0 (October 1, 2009)
* Specification available from http://jcp.org/en/jsr/detail?id=317
*/
// $Id: JoinColumn.java 20957 2011-06-13 09:58:51Z stliu $
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 a column for joining an entity association or element
* collection. If the <code>JoinColumn</code> annotation itself is
* defaulted, a single join column is assumed and the default values
* apply.
*
* <pre>
* Example:
*
* @ManyToOne
* @JoinColumn(name="ADDR_ID")
* public Address getAddress() { return address; }
*
*
* Example: unidirectional one-to-many association using a foreign key mapping
*
* // In Customer class
* @OneToMany
* @JoinColumn(name="CUST_ID") // join column is in table for Order
* public Set<Order> getOrders() {return orders;}
* </pre>
*
* @see ManyToOne
* @see OneToMany
* @see OneToOne
* @see JoinTable
* @see CollectionTable
*
* @since Java Persistence 1.0
*/
@Target({METHOD, FIELD})
@Retention(RUNTIME)
public @interface JoinColumn {
/**
* (Optional) The name of the foreign key column.
* The table in which it is found depends upon the
* context.
* <ul>
* <li>If the join is for a OneToOne or ManyToOne
* mapping using a foreign key mapping strategy,
* the foreign key column is in the table of the
* source entity or embeddable.
* <li> If the join is for a unidirectional OneToMany mapping
* using a foreign key mapping strategy, the foreign key is in the
* table of the target entity.
* <li> If the join is for a ManyToMany mapping or for a OneToOne
* or bidirectional ManyToOne/OneToMany mapping using a join
* table, the foreign key is in a join table.
* <li> If the join is for an element collection, the foreign
* key is in a collection table.
*</ul>
*
* <p> Default (only applies if a single join column is used):
* The concatenation of the following: the name of the
* referencing relationship property or field of the referencing
* entity or embeddable class; "_"; the name of the referenced
* primary key column.
* If there is no such referencing relationship property or
* field in the entity, or if the join is for an element collection,
* the join column name is formed as the
* concatenation of the following: the name of the entity; "_";
* the name of the referenced primary key column.
*/
String name() default "";
/**
* (Optional) The name of the column referenced by this foreign
* key column.
* <ul>
* <li> When used with entity relationship mappings other
* than the cases described here, the referenced column is in the
* table of the target entity.
* <li> When used with a unidirectional OneToMany foreign key
* mapping, the referenced column is in the table of the source
* entity.
* <li> When used inside a <code>JoinTable</code> annotation,
* the referenced key column is in the entity table of the owning
* entity, or inverse entity if the join is part of the inverse
* join definition.
* <li> When used in a <code>CollectionTable</code> mapping, the
* referenced column is in the table of the entity containing the
* collection.
* </ul>
*
* <p> Default (only applies if single join column is being
* used): The same name as the primary key column of the
* referenced table.
*/
String referencedColumnName() default "";
/**
* (Optional) Whether the property 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 is only a single field. It is not necessary to
* explicitly specify this for a join column that corresponds to a
* primary key that is part of a foreign key.
*/
boolean unique() default false;
/** (Optional) Whether the foreign key column is nullable. */
boolean nullable() default true;
/**
* (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 for the column.
*/
String columnDefinition() default "";
/**
* (Optional) The name of the table that contains
* the column. If a table is not specified, the column
* is assumed to be in the primary table of the
* applicable entity.
*
* <p> Default:
* <ul>
* <li> If the join is for a OneToOne or ManyToOne mapping
* using a foreign key mapping strategy, the name of the table of
* the source entity or embeddable.
* <li> If the join is for a unidirectional OneToMany mapping
* using a foreign key mapping strategy, the name of the table of
* the target entity.
* <li> If the join is for a ManyToMany mapping or
* for a OneToOne or bidirectional ManyToOne/OneToMany mapping
* using a join table, the name of the join table.
* <li> If the join is for an element collection, the name of the collection table.
* </ul>
*/
String table() default "";
/**
* (Optional) The foreign key constraint specification for the join column. This is used only if table generation
* is in effect. Default is provider defined.
*
* @return The foreign key specification
*/
ForeignKey foreignKey() default @ForeignKey();
}