jakarta.persistence.OneToMany Maven / Gradle / Ivy
/*
* Copyright (c) 2008, 2023 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 jakarta.persistence;
import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
/**
* Specifies a many-valued association with one-to-many multiplicity.
*
* If the collection is defined using generics to specify the element
* type, the associated target entity type need not be specified; otherwise
* the target entity class must be specified. If the relationship is
* bidirectional, the {@link #mappedBy} element must be used to specify
* the relationship field or property of the entity that is the owner of
* the relationship.
*
*
A {@code OneToMany} association usually maps a foreign key column
* or columns in the table of the associated entity. This mapping may
* be specified using the {@link JoinColumn} annotation. Alternatively,
* a unidirectional {@code OneToMany} association is sometimes mapped
* to a join table using the {@link JoinTable} annotation.
*
*
The {@code OneToMany} annotation may be used within an embeddable
* class contained within an entity class to specify a relationship to a
* collection of entities. If the relationship is bidirectional, the
* {@link #mappedBy} element must be used to specify the relationship
* field or property of the entity that is the owner of the relationship.
*
*
When the collection is a {@link java.util.Map}, the {@link #cascade}
* element and the {@link #orphanRemoval} element apply to the map value.
*
*
*
Example 1: One-to-Many association using generics
* {@snippet :
* // In Customer class:
*
* @OneToMany(cascade = ALL, mappedBy = "customer")
* public Set getOrders() { return orders; }
*
* // In Order class:
*
* @ManyToOne
* @JoinColumn(name = "CUST_ID", nullable = false)
* public Customer getCustomer() { return customer; }
* }
*
* Example 2: One-to-Many association without using generics
* {@snippet :
* // In Customer class:
*
* @OneToMany(targetEntity = com.acme.Order.class, cascade = ALL,
* mappedBy = "customer")
* public Set getOrders() { return orders; }
*
* // In Order class:
*
* @ManyToOne
* @JoinColumn(name = "CUST_ID", nullable = false)
* public Customer getCustomer() { return customer; }
* }
*
*
Example 3: Unidirectional One-to-Many association using a foreign key mapping
* {@snippet :
* // In Customer class:
*
* @OneToMany(orphanRemoval = true)
* @JoinColumn(name = "CUST_ID") // join column is in table for Order
* public Set getOrders() { return orders; }
*
* }
*
* @since 1.0
*/
@Target({METHOD, FIELD})
@Retention(RUNTIME)
public @interface OneToMany {
/**
* (Optional) The entity class that is the target of the
* association. Optional only if the collection property is
* defined using Java generics. Must be specified otherwise.
*
* Defaults to the parameterized type of the collection when
* defined using generics.
*/
Class targetEntity() default void.class;
/**
* (Optional) The operations that must be cascaded to the target
* of the association.
*
Defaults to no operations being cascaded.
*
When the target collection is a {@link java.util.Map},
* the {@code cascade} element applies to the map value.
*/
CascadeType[] cascade() default {};
/** (Optional) Whether the association should be lazily loaded or
* must be eagerly fetched. The EAGER strategy is a requirement on
* the persistence provider runtime that the associated entities
* must be eagerly fetched. The LAZY strategy is a hint to the
* persistence provider runtime.
*/
FetchType fetch() default FetchType.LAZY;
/**
* The field that owns the relationship. Required unless
* the relationship is unidirectional.
*/
String mappedBy() default "";
/**
* (Optional) Whether to apply the remove operation to entities
* that have been removed from the relationship and to cascade
* the remove operation to those entities.
* @since 2.0
*/
boolean orphanRemoval() default false;
}