Use of set tag in Hibernate mapping file?

[Joe Harry]

Guys,

What exactly happens when we have a <set> tag and a link table when the relationship is many to many? I'm a little bit confused over it. Please help!

[Joe Harry]

Any help guys?

[Paul Sturrock]

Not sure what you mean. Are you confuesed how it define many-to-many associations? Or are you asking something else?

[Joe Harry]

Yes Paul, I'm confused on how to define many-to-many relations...

[Paul Sturrock]

The best place to find this out is the Hibernate documentation's chapter on associtaions. From those docs, a unidirectional many-to-many association:

<class name="Person">
    <id name="id" column="personId">
        <generator class="native"/>
    </id>
    <set name="addresses" table="PersonAddress">
        <key column="personId"/>
        <many-to-many column="addressId"
            class="Address"/>
    </set>
</class>
 
<class name="Address">
    <id name="id" column="addressId">
        <generator class="native"/>
    </id>
</class>
 
create table Person ( personId bigint not null primary key )
create table PersonAddress ( personId bigint not null, addressId bigint not null, primary key (personId, addressId) )
create table Address ( addressId bigint not null primary key )

[Joe Harry]

I'll try to go through it and if I feel still not clear, I will come back here and ask you guys. Thanks!