JPA Annotation

ManyToMany

Target: METHOD, FIELD
Implemented Interfaces:
Annotation
Specifies a many-valued association with many-to-many multiplicity, mapping to an intermediate table called the join table.

Every many-to-many association has two sides, the owning side and the non-owning, or inverse, side. The join table is specified on the owning side. If the association is bidirectional, either side may be designated as the owning side, and the non-owning side must use the ManyToMany.mappedBy element of the ManyToMany annotation to specify the relationship field or property of the owning side.

The join table for the relationship, if not defaulted, is specified on the owning side. The JoinTable annotation specifies a mapping to a database table.

The ManyToMany annotation may be used within an embeddable class contained within an entity class to specify a relationship to a collection of entities. If the relationship is bidirectional and the entity containing the embeddable class is the owner of the relationship, the non-owning side must use the ManyToMany.mappedBy element of the ManyToMany annotation to specify the relationship field or property of the embeddable class. 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 :
 // In Customer class:
See Also:
JoinTable
Since:
JPA 1.0

Public Annotation Attributes

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

When the target collection is a java.util.Map, the cascade element applies to the map value.

Defaults to no operations being cascaded.

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

Since:
JPA 1.0
String mappedBy default ""
The field that owns the relationship.
Required unless the relationship is unidirectional.
Since:
JPA 1.0
Class<?> targetEntity default void.class
(Optional) The entity class that is the target of the association.
Optional only if the collection-valued relationship property is defined using Java generics. Must be specified otherwise.

Defaults to the parameterized type of the collection when defined using generics.

Since:
JPA 1.0