Jakarta Persistence (JPA) Annotation Type

jakarta.persistence.ManyToOne

Implemented Interfaces:
Annotation
Target:
Method, Field
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 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.

A ManyToOne association usually maps a foreign key column or columns. This mapping may be specified using the JoinColumn annotation. Alternatively, an optional OneToOne association is sometimes mapped to a join table using the JoinTable annotation.

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 manages;
 }
Since:
Jakarta Persistence (JPA) 1.0

Annotation Elements

Class<?> targetEntity
(Optional) The entity class that is the target of the association.

Defaults to the type of the field or property that stores the association.

Default:
void/class
Since:
Jakarta Persistence (JPA) 1.0
CascadeType[] cascade
(Optional) The operations that must be cascaded to the target of the association.

By default no operations are cascaded.

Default:
{}
Since:
Jakarta Persistence (JPA) 1.0
FetchType fetch
(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.

If not specified, defaults to EAGER.

Default:
FetchType.EAGER
Since:
Jakarta Persistence (JPA) 1.0
boolean optional
(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 not null.

Default:
true
Since:
Jakarta Persistence (JPA) 1.0

Additional JDK methods inherited from java.lang.annotation.Annotation

annotationType(), equals(Object), hashCode(), toString()