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/*
 * 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; }





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