Neet to use property-ref with one-to-many composite key.

reshma_k · **Joined:** Wed May 25, 2005 11:03 am **Posts:** 13

Hi,

I have a problem wherein I need to use a property-ref tag in one-to-many association.

Following entities are involved:

-------

cm_step
step_id
step_version_d
step_rule_set_id
step_rule_set_version

cm_rule_set
rule_set_id
rule_set_version_id

-------

step_rule_set_id maps to rule_set_id and step_rule_set_version_id maps to rule_set_version_id. Although this is a perfect example of many-to-one association from cm_step to cm_rule_set, I want cm_rule_set object to be deleted when it is unreferenced from cm_step object (orphan deletion). This is not possible with one-to-one or many-to-one association. Hence I have to implement one-to-many from cm_step to cm_rule_set.

<key> element can appear only once in <Set> tag, and <key> element has got 'column' and 'property-ref' support for one column only. Now I cannot use property-ref as I have composite foreign key.

How can I implement this relationship?
Please suggest any other approach if possible.

Thanks in advance!

~ Reshma

Hibernate version:3.0[/b]

mojarrell · **Posted:** Tue Jun 27, 2006 12:08 pm

As to the orphan deletion part of your question, it should be easy to implement a separate job that deletes orphans periodically. If you do that then you can map the entities as they really are rather than forcing them into a mapping that might not make sense. Orphan deletion seems counter intuitive to me in this situation.

As to the mapping of the association from cm_step to cm_rule_set, here's how I did it and it seems to work well on my sample program (note the column elements within the key):

Code:

    <class name="CmStep" table="CM_STEP">
        <composite-id>
            <key-property name="stepId" column="STEP_ID" />
            <key-property name="stepVersionId" column="STEP_VERSION_ID" />
        </composite-id>
        <many-to-one name="cmRuleSet" lazy="false">
            <column name="STEP_RULE_SET_ID" />
            <column name="STEP_RULE_SET_VERSION_ID" />
        </many-to-one>
    </class>

    <class name="CmRuleSet" table="CM_RULE_SET">
        <composite-id>
            <key-property name="ruleSetId" column="RULE_SET_ID" />
            <key-property name="ruleSetVersionId" column="RULE_SET_VERSION_ID" />
        </composite-id>
        <set name="cmSteps" inverse="true" lazy="false">
            <key>
                <column name="STEP_RULE_SET_ID"/>
                <column name="STEP_RULE_SET_VERSION_ID" />
            </key>
            <one-to-many class="CmStep" />
        </set>
    </class>

Hope this helps,

reshma_k · **Joined:** Wed May 25, 2005 11:03 am **Posts:** 13

Hi,

The mapping you specified is already implemented in the application. The orphan deletion problem was encountered later and hence we tried to change the mapping. Since it is not a good practice to manipulate association this way, I guess what you have suggested is right. I'll have to write a job that periodically purges orphan rule sets.

Thanks for your help.

~ Reshma

tenwit · **Joined:** Thu Dec 23, 2004 9:08 pm **Posts:** 2008

There is an alternative. You can map multiple columns as a single property, thus allowing property-ref (which refers to properties, not columns) to refer to them. Check out the ref docs section 5.1.14 to see if this is appropriate for you.

reshma_k · **Joined:** Wed May 25, 2005 11:03 am **Posts:** 13

Hey tenwit

Thanks for your help. I tried that out. But due to some problem, I am not able to retrieve the association properly. And now we have decided to write a separate job for purging orphan rule set objects keeping relationship many-to-one

Thanks anyways

~ Reshma