hi ,
i am new in Hibernate, getting confused by mapping a many-to-many relationship with a atrribute. if there's somebody can help?

have 3 tables:
Person: can attend many projects(PK:PersonID)
Project: contains many persons(PK:ProjectID)
the last table is Person_Project, which has PersonID(PK;FK), ProjectID(PK;FK), and a extra roleName.

in both of my person and Project mapping file i have this:
Person.hbm.xml
<set name="projects" table="TMP_PERS_SUBP" lazy="true">
<key column="PERSONID"/>
<many-to-many class="mapping.Project" column="PROJECTID"/>
</set>
Project.hbm.xml
<set name="persons" table="TMP_PERS_SUBP" lazy="true">
<key column="PROJECTID"/>
<many-to-many class="mapping.Person" column="PERSONID"/>
</set>

but what should i do with the attribute roleName?

You have two options:

1) An intermediate Entity Class for the join table with one-to-many mappings


2) Using a collection of components which is described here:
http://www.hibernate.org/hib_docs/v3/re ... ollections
You should be aware that bidirectional navigation is NOT supported with this approach.
This mapping is copy pasted from the Hibernate documentation, I have just marked the interesting part of this kind of mapping.

<class name="eg.Order" .... >
....
<set name="purchasedItems" table="purchase_items" lazy="true">
<key column="order_id">
<composite-element class="eg.Purchase">
<property name="purchaseDate"/>
<property name="price"/>
<property name="quantity"/>
<many-to-one name="item" class="eg.Item"/>
</composite-element>
</set>
</class>

thanks a lot. because i have not much idea of the whole thing yet, i will try the first option.

I think using option 1 is a good choice for you since it also supports bidirectional navigation!

what should i do with the two PK(FK)s now? :-(

i mean, do i need to generate a PK for this relationtable extra?

Hi, I get exactly same problem with you.

Could you please explain me the first option?

Use the two reference fields as primary key.