/*
* 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.FIELD;
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)
CustomerRecord customerRecord;
// On CustomerRecord class:
@OneToOne(optional=false, mappedBy="customerRecord")
Customer 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
/**
* 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
* <code>mappedBy</code> element of the <code>OneToOne</code> annotation to specify the relationship field or
* property of the owning side.
* <p>
* The <code>OneToOne</code> 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
* <code>mappedBy</code> element of the <code>OneToOne</code> annotation to specify the relationship field or
* property of the embeddable class. The dot (".") notation syntax must be used in the <code>mappedBy</code>
* 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.
* <p>
* <pre>
* 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)
* CustomerRecord customerRecord;
*
* // On CustomerRecord class:
*
* @OneToOne(optional=false, mappedBy="customerRecord")
* Customer 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;
* ...
* }
*
* </pre>
*
* @since Java Persistence 1.0
*/
@Target({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.
Returns: target entity
/**
* (Optional) The entity class that is the target of the association.
* <p>
* 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.
Returns: cascade type
/**
* (Optional) The operations that must be cascaded to the target of the association.
* <p>
* 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.
Returns: fetch type
/**
* (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.
Returns: optional?
/**
* (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.
Returns: mappedby
/**
* (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.
Returns: whether to remove orphans Since: Java Persistence 2.0
/**
* (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.
*
* @return whether to remove orphans
* @since Java Persistence 2.0
*/
boolean orphanRemoval() default false;
}