Annotation Interface ManyToMany
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. If the relationship is
bidirectional, the non-owning side must use the 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 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
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: // In Customer class: @ManyToMany @JoinTable(name="CUST_PHONES") public Set<PhoneNumber> getPhones() { return phones; } // In PhoneNumber class: @ManyToMany(mappedBy="phones") public Set<Customer> getCustomers() { return customers; } Example 2: // In Customer class: @ManyToMany(targetEntity=com.acme.PhoneNumber.class) public Set getPhones() { return phones; } // In PhoneNumber class: @ManyToMany(targetEntity=com.acme.Customer.class, mappedBy="phones") public Set getCustomers() { return customers; } Example 3: // In Customer class: @ManyToMany @JoinTable(name="CUST_PHONE", joinColumns= @JoinColumn(name="CUST_ID", referencedColumnName="ID"), inverseJoinColumns= @JoinColumn(name="PHONE_ID", referencedColumnName="ID") ) public Set<PhoneNumber> getPhones() { return phones; } // In PhoneNumberClass: @ManyToMany(mappedBy="phones") public Set<Customer> getCustomers() { return customers; }
- Since:
- Java Persistence 1.0
- See Also:
-
Optional Element Summary
Modifier and TypeOptional ElementDescription(Optional) The operations that must be cascaded to the target of the association.(Optional) Whether the association should be lazily loaded or must be eagerly fetched.The field that owns the relationship.(Optional) The entity class that is the target of the association.
-
Element Details
-
targetEntity
Class targetEntity(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.
- Default:
- void.class
-
cascade
CascadeType[] cascade(Optional) The operations that must be cascaded to the target of the association.When the target collection is a
java.util.Map
, thecascade
element applies to the map value.Defaults to no operations being cascaded.
- Default:
- {}
-
fetch
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 entities must be eagerly fetched. The LAZY strategy is a hint to the persistence provider runtime.- Default:
- LAZY
-
mappedBy
String mappedByThe field that owns the relationship. Required unless the relationship is unidirectional.- Default:
- ""
-