ManyToMany (Java EE 5 SDK) - Java Platform, Enterprise Edition v5.0 API Specifications

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SUMMARY: REQUIRED | OPTIONAL

DETAIL: ELEMENT

javax.persistence
Annotation Type ManyToMany

@Target(value={METHOD,FIELD}) @Retention(value=RUNTIME) public @interface ManyToMany

Defines a many-valued association with many-to-many multiplicity. If the Collection is defined using generics to specify the element type, the associated target entity class does not need to be specified; otherwise it must be specified.

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.

The same annotation elements for the OneToMany annotation apply to the ManyToMany annotation.


    Example 1:

    In Customer class:

    @ManyToMany
    @JoinTable(name="CUST_PHONES")
    public Set getPhones() { return phones; }

    In PhoneNumber class:

    @ManyToMany(mappedBy="phones")
    public Set 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 getPhones() { return phones; }

    In PhoneNumberClass:

    @ManyToMany(mappedBy="phones")
    public Set getCustomers() { return customers; }

Since:: Java Persistence 1.0

Optional Element Summary

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.

Optional Element Summary
`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.

targetEntity

public abstract Class targetEntity

(Optional) The entity class that is the target of the association. Optional only if the collection 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

public abstract CascadeType[] cascade

(Optional) The operations that must be cascaded to the target of the association.

Defaults to no operations being cascaded.

Default:: {}

fetch

public abstract FetchType fetch

(Optional) Whether the association should be lazily loaded or must be eagerly fetched. The EAGER strategy is a requirement on the persistenceprovider runtime that the associatedentities must be eagerly fetched. The LAZY strategy is a hint to the persistence provider runtime.

Default:: LAZY

mappedBy

public abstract String mappedBy

The field that owns the relationship. Required unless the relationship is unidirectional.

Default:: ""