javax.persistence.ManyToOne 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 class that has many-to-one multiplicity. It is not
* normally 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 OneToMany
* entity side must use the mappedBy element to specify the relationship field or property of
* the entity that is the owner of the relationship.
*
* The 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
* OneToMany entity side must use the mappedBy element of the OneToMany
* annotation to specify the relationship field or property of the embeddable field or property on the owning
* side of the relationship. 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:
*
* @ManyToOne(optional=false)
* @JoinColumn(name="CUST_ID", nullable=false, updatable=false)
* public Customer getCustomer() { return customer; }
*
*
* Example 2:
*
* @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<Employee> manages;
* }
*
*
* @since Java Persistence 1.0
*/
@Target({ANNOTATION_TYPE, 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.
* @return The 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 The 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 The 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 Whether this is optional
*/
boolean optional() default true;
}