com.easycodebox.common.jpa

注释类型 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; }
 

从以下版本开始:

Java Persistence 1.0

可选元素概要

可选元素

限定符和类型	可选元素和说明
FetchType	fetch 此功能暂未实现
String	mappedBy The field that owns the relationship.
Class	targetEntity (Optional) The entity class that is the target of the association.

元素详细资料

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.

默认值:

void.class

fetch

public abstract FetchType fetch

此功能暂未实现

默认值:

com.easycodebox.common.jpa.FetchType.LAZY

mappedBy

public abstract String mappedBy

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

默认值:

""