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How to configure many-to-many w/ data on relationship

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sniederb

Post subject: How to configure many-to-many w/ data on relationship

Posted: Mon Nov 20, 2006 8:46 am

Newbie

Joined: Fri Nov 17, 2006 9:40 am
Posts: 11
Location: Switzerland

Hi all

We need to configure a few many-to-many relationships in Hibernate. I believe I get the concept of a "simple" many-to-many relationship. However, I haven't found any examples on how to configure such a relationships if the many-to-many map itself contains data about the mapping. Say I have:

Table INVOICE (ID, INVOICENUMBER, AMOUNT)
Table PAYMENT (ID, PAYMENTDATE, AMOUNT)

A many-to-many relation between the two such that:

One PAYMENT can be distributed across multiple INVOICEs, one INVOICE can be paid by multiple PAYMENTs. AND - here's the thing - if a PAYMENT is distributed across multiple INVOICEs, the INVOICE-PAYMENT-MAP contains the amount assigned from a payment to an invoice. The business logic will acertain the the sum of all those amounts equals the total payment amount.

PAYMENT: 500.-
INVOICE A: 200.-, INVOICE-PAYMENT-MAP.AMOUNT = 200
INVOICE B: 300.-, INVOICE-PAYMENT-MAP.AMOUNT = 300

How do I configure this in Hibernate? (Please supply chapter or links with RTFM-comments)

Thanks
Simon

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mikeh

Post subject: Re: How to configure many-to-many w/ data on relationship

Posted: Mon Nov 20, 2006 10:08 am

Newbie

Joined: Wed Jan 04, 2006 5:17 am
Posts: 4

You would need to create a third object InvoicePayment that would hold the additional information, in this case the amount of the payment allocated to the specific invoice. The relationships would also change: you would have a one-to-many relationship between Invoice and InvoicePayment and a many-to-one relationship between InvoicePayment and Payment.

Hope that helps!

Mike.

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sniederb

Post subject:

Posted: Mon Nov 20, 2006 11:50 am

Newbie

Joined: Fri Nov 17, 2006 9:40 am
Posts: 11
Location: Switzerland

Hi Mike

Thnkas fou your input. Yes, we've been playing around with configurations such as

Code:

<hibernate-mapping>
    <class name="net.umbrella.data.model.PaymentInvoiceMapModel" table="PAYMENT_INVOICE_MAP">
        <composite-id name="id" class="net.umbrella.data.model.PaymentInvoiceMapIdModel">
            <key-property name="paymentid" type="int">
                <column name="PAYMENTID" />
            </key-property>
            <key-property name="invoiceid" type="int">
                <column name="INVOICEID" />
            </key-property>
        </composite-id>
        <many-to-one name="bookings" class="net.umbrella.data.model.BookingModel" update="false" insert="false" fetch="select">
            <column name="PAYMENTID" not-null="true" />
        </many-to-one>
        <many-to-one name="invoices" class="net.umbrella.data.model.InvoiceModel" update="false" insert="false" fetch="select">
            <column name="INVOICEID" not-null="true" />
        </many-to-one>
        <property name="amount" type="java.lang.Double">
            <column name="AMOUNT" scale="4" not-null="true" />
        </property>
    </class>
</hibernate-mapping>

The problem we most often encountered was: deleting an invoice deletes the map entry from the invoice side, but not from the payment side. Result: Hibernate exception along the line of "deleted object would be re-saved"

Cheers
Simon

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