javax.persistence.ManyToOne Maven / Gradle / Ivy
package javax.persistence;
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;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
/**
* 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)
* 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({ METHOD, FIELD })
@Retention(RUNTIME)
public @interface ManyToOne {
/**
* (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 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.
*/
FetchType fetch() default EAGER;
/**
* (Optional) Whether the association is optional. If set to false then a non-null relationship must always exist.
*/
boolean optional() default true;
/**
* (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;
}