@Target(value={METHOD,FIELD}) @Retention(value=RUNTIME) public @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; }
JoinTable
Modifier and Type | Optional Element and Description |
---|---|
CascadeType[] |
cascade
(Optional) The operations that must be cascaded to the target of the association.
|
FetchType |
fetch
(Optional) Whether the association should be lazily loaded or must be eagerly fetched.
|
String |
mappedBy
The field that owns the relationship.
|
Class |
targetEntity
(Optional) The entity class that is the target of the association.
|
public abstract Class targetEntity
Defaults to the parameterized type of the collection when defined using generics.
public abstract CascadeType[] cascade
When the target collection is a java.util.Map
, the cascade
element
applies to the map value.
Defaults to no operations being cascaded.
public abstract FetchType fetch
public abstract String mappedBy
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