/*
* 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 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 used 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)
Customer 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
/**
* 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 <code>OneToMany</code>
* entity side must used the <code>mappedBy</code> element to specify the relationship field or property of
* the entity that is the owner of the relationship.
* <p>
* The <code>ManyToOne</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, the non-owning
* <code>OneToMany</code> entity side must use the <code>mappedBy</code> element of the <code>OneToMany</code>
* 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 <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:
*
* @ManyToOne(optional=false)
* @JoinColumn(name="CUST_ID", nullable=false, updatable=false)
* Customer 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;
* }
*
* </pre>
*
* @since Java Persistence 1.0
*/
@Target({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.
Returns: The 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 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.
Returns: The cascade type
/**
* (Optional) The operations that must be cascaded to the target of the association.
* <p>
* 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.
Returns: The 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 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.
Returns: Whether this is optional
/**
* (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;
}