JPA Annotation

ManyToOne

Target: METHOD, FIELD
Implemented Interfaces:
Annotation
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:

 {@snippet :
Since:
JPA 1.0

Public Annotation Attributes

CascadeType[] cascade default {}
(Optional) The operations that must be cascaded to the target of the association.

By default no operations are cascaded.

Since:
JPA 1.0
FetchType fetch default FetchType.EAGER
(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.

Since:
JPA 1.0
boolean optional default true
(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.

Since:
JPA 1.0
Class<?> targetEntity default void.class
(Optional) The entity class that is the target of the association.

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

Since:
JPA 1.0