javax.persistence.OneToOne Maven / Gradle / Ivy
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/*
* Copyright (c) 2008, 2009, 2011 Oracle, Inc. 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.
*/
package javax.persistence;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import static javax.persistence.FetchType.EAGER;
/**
* Defines a single-valued association to another entity that has one-to-one multiplicity. It is not normally
* 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
* mappedBy element of the OneToOne annotation to specify the relationship field or
* property of the owning side.
*
* The 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
* mappedBy element of the OneToOne annotation to specify the relationship field or
* property of the embeddable class. The dot (".") notation syntax must be used in the 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
*
* // 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.
*
* // 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.
*
* @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 Java Persistence 1.0
*/
@Target({ANNOTATION_TYPE, 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.
* @return target entity
*/
Class targetEntity() default void.class;
/**
* (Optional) The operations that must be cascaded to the target of the association.
*
* By default no operations are cascaded.
* @return cascade type
*/
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 entity must be
* eagerly fetched. The LAZY strategy is a hint to the persistence provider runtime.
* @return fetch type
*/
FetchType fetch() default EAGER;
/**
* (Optional) Whether the association is optional. If set to false then a non-null relationship must
* always exist.
* @return optional?
*/
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.
* @return mappedby
*/
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 Java Persistence 2.0
* @return whether to remove orphans
*/
boolean orphanRemoval() default false;
}