jakarta.persistence.ManyToOne 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.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
/**
* Specifies a single-valued association to another entity class that
* has many-to-one multiplicity. It is not usually necessary to specify
* the 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
* {@link OneToMany} entity side must use the {@link OneToMany#mappedBy
* mappedBy} element to specify the relationship field or property of the
* entity that is the owner of the relationship.
*
*
A {@code ManyToOne} association usually maps a foreign key column
* or columns. This mapping may be specified using the {@link JoinColumn}
* annotation. Alternatively, an optional {@code OneToOne} association is
* sometimes mapped to a join table using the {@link JoinTable} annotation.
*
*
The {@code ManyToOne} 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, the non-owning
* {@link OneToMany} entity side must use the {@code mappedBy} element of
* the {@code OneToMany} annotation to specify the relationship field or
* property of the embeddable field or property on the owning side of the
* relationship. The dot ({@code .}) notation syntax must be used in the
* {@code 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:
* {@snippet :
* @ManyToOne(optional = false)
* @JoinColumn(name = "CUST_ID", nullable = false, updatable = false)
* public Customer getCustomer() { return customer; }
* }
*
*
Example 2:
* {@snippet :
* @Entity
* public class Employee {
* @Id
* int id;
* @Embedded
* JobInfo jobInfo;
* ...
* }
*
* @Embeddable
* public class JobInfo {
* String jobDescription;
* @ManyToOne
* ProgramManager pm; // Bidirectional
* }
*
* @Entity
* public class ProgramManager {
* @Id
* int id;
* @OneToMany(mappedBy = "jobInfo.pm")
* Collection manages;
* }
* }
*
* @since 1.0
*/
@Target({METHOD, FIELD})
@Retention(RUNTIME)
public @interface ManyToOne {
/**
* (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.
*
*
May be used in schema generation to infer that the
* mapped foreign key column is {@link JoinColumn#nullable
* not null}.
*/
boolean optional() default true;
}