How to prevent delete of object with associated objects?

oliverchua · **Joined:** Tue Nov 16, 2004 10:18 pm **Posts:** 8

Hibernate version:
3.0

Mapping documents:

Code:

<hibernate-mapping>
    <class
        name="com.tougher.intranet.employee.unit.Unit"
        table="Unit">

        <id
            name="unitCode"
            column="unitCode"
            type="java.lang.Long">
            <generator class="native">
            </generator>
        </id>

        <property
            name="unitName"
            type="java.lang.String"
            update="true"
            insert="true"
            column="unitName"/>

        <many-to-one
            name="superUnit"
            class="com.tougher.intranet.employee.unit.Unit"
            cascade="none"
            outer-join="auto"
            update="true"
            insert="true"
            column="superUnitCode"/>

        <set
            name="subUnits"
            lazy="false"
            cascade="none"
            sort="com.tougher.intranet.employee.unit.Unit">
            <key
                column="superUnitCode">
            </key>
            <one-to-many
                  class="com.tougher.intranet.employee.unit.Unit"/>
        </set>
    </class>
</hibernate-mapping>

Code between sessionFactory.openSession() and session.close():

Full stack trace of any exception that occurs:

Name and version of the database you are using:

The generated SQL (show_sql=true):

Debug level Hibernate log excerpt:

I have a recursive relationship... Units associated to superUnits.
When I delete a unit that is a superUnit of other units,
what happens is that the unit is deleted and the subUnit's referenece column becomes null...
Is this is the expected behavior?
What should I change in my mapping.xml file to prevent delete if there are still objects associated to the object in question?

thanks.

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

Nothing in your mapping. In your delete method, add "if (!getSubUnits().isEmpty()) { return; }", or equivalent.

jt_1000 · **Posted:** Tue Feb 28, 2006 10:37 pm

oliverchua wrote:

When I delete a unit that is a superUnit of other units,
what happens is that the unit is deleted and the subUnit's referenece column becomes null...
Is this is the expected behavior?

in the <set ... put cascade="delete-orphan"
will take care of deleting the dangling child records.

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

He wants it the other way around: to not delete a unit if it has subunits :)

There is nothing you can do in the mapping to implement this, as it is very non-standard. For one thing, if you issue a delete statement, you expect either a row to be deleted, or an SQL exception to be reported. If you want to conditionally not delete the row, you'll have to implement that in business logic.

oliverchua · **Joined:** Tue Nov 16, 2004 10:18 pm **Posts:** 8

thanks tenwit,

you nailed it.
thanks!

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

It's easier, and more appreciated, to just click the "Yes the post helped" link in the helpful post :)

jt_1000 · **Posted:** Wed Mar 01, 2006 12:52 am

You asked two questions.

Glad to hear tenwits response worked for your second question -- I was answering your first question.

Quote:

Is this is the expected behavior?

Which to elaborate a llittle bit on: Yes what you experienced is expected, and you can use the suggestion that I gave to delete them if you want to.

Hope that helps you...

jt_1000 · **Posted:** Wed Mar 01, 2006 1:18 pm

After thinking about the 2nd question a bit more - I realized that have implemented in my testing another solution (with hibernate) that you can do in your mapping.

Try:
<sql-delete callable="true">{? = deleteItem(?)}</sql-delete>

Then in your db-function you can raise an application error if there are children or subordinate objects or any other conditions that violate your business rules - however, I'd like to add one more item. It is probably best to set this type of constraint up in the database itself such that you can't delete a parent that has children - this will also raise a database foreign key exception and also suite your needs.