jakarta.persistence.OneToOne 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 single-valued association to another entity class that
* has one-to-one multiplicity. It is not usually necessary to specify
* the associated target entity explicitly, since it can usually be
* inferred from the type of the object being referenced.
*
* If the relationship is bidirectional, the non-owning side must
* use the {@link #mappedBy} element of the {@code OneToOne} annotation
* to specify the relationship field or property of the owning side.
*
*
A {@code OneToOne} association usually maps a unique foreign key
* relationship, either a foreign key column or columns with a unique
* constraint, or a relationship via a shared primary key. The
* {@link JoinColumn} annotation may be used to map the foreign key
* column or columns. Alternatively, an optional {@code OneToOne}
* association is sometimes mapped to a join table using the
* {@link JoinTable} annotation.
*
*
The {@code OneToOne} annotation may be used within an embeddable
* class to specify a relationship from the embeddable class to an
* entity class. If the relationship is bidirectional and the entity
* containing the embeddable class is on the owning side of the
* relationship, the non-owning side must use the {@link #mappedBy}
* element of the {@code OneToOne} annotation to specify the relationship
* field or property of the embeddable class. The dot ({@code .}) notation
* syntax must be used in the {@link #mappedBy} element to indicate the
* relationship attribute within the embedded attribute. The value of
* each identifier used with the dot notation is the name of the
* respective embedded field or property.
*
*
Example 1: One-to-one association that maps a foreign key column
* {@snippet :
* // On Customer class:
*
* @OneToOne(optional = false)
* @JoinColumn(name = "CUSTREC_ID", unique = true, nullable = false, updatable = false)
* public CustomerRecord getCustomerRecord() { return customerRecord; }
*
* // On CustomerRecord class:
*
* @OneToOne(optional = false, mappedBy = "customerRecord")
* public Customer getCustomer() { return customer; }
* }
*
*
Example 2: One-to-one association that assumes both the source and
* target share the same primary key values.
* {@snippet :
* // On Employee class:
*
* @Entity
* public class Employee {
* @Id
* Integer id;
*
* @OneToOne
* @MapsId
* EmployeeInfo info;
* ...
* }
*
* // On EmployeeInfo class:
*
* @Entity
* public class EmployeeInfo {
* @Id
* Integer id;
* ...
* }
* }
*
*
Example 3: One-to-one association from an embeddable class to another
* entity.
* {@snippet :
* @Entity
* public class Employee {
* @Id
* int id;
* @Embedded
* LocationDetails location;
* ...
* }
*
* @Embeddable
* public class LocationDetails {
* int officeNumber;
* @OneToOne
* ParkingSpot parkingSpot;
* ...
* }
*
* @Entity
* public class ParkingSpot {
* @Id
* int id;
* String garage;
* @OneToOne(mappedBy = "location.parkingSpot")
* Employee assignedTo;
* ...
* }
* }
*
* @since 1.0
*/
@Target({METHOD, FIELD})
@Retention(RUNTIME)
public @interface OneToOne {
/**
* (Optional) The entity class that is the target of the
* association.
*
*
Defaults to the type of the field or property
* that stores the association.
*/
Class targetEntity() default void.class;
/**
* (Optional) The operations that must be cascaded to the
* target of the association.
*
*
By default no operations are cascaded.
*/
CascadeType[] cascade() default {};
/**
* (Optional) Whether the association should be lazily
* loaded or must be eagerly fetched.
*
* - The {@link FetchType#EAGER EAGER} strategy is a
* requirement on the persistence provider runtime
* that the associated entity must be eagerly fetched.
*
- The {@link FetchType#LAZY LAZY} strategy is a hint
* to the persistence provider runtime.
*
*
* If not specified, defaults to {@code EAGER}.
*/
FetchType fetch() default FetchType.EAGER;
/**
* (Optional) Whether the association is optional. If set
* to false then a non-null relationship must always exist.
*/
boolean optional() default true;
/**
* (Optional) The field that owns the relationship. This
* element is only specified on the inverse (non-owning)
* side of the association.
*/
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;
}