Question

I’m trying to set up a project using hibernate.I have two tables : Users and Address with the following mappings :

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
    Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<hibernate-mapping>
    <class name="Address" table="ADDRESS" >
        <cache usage="read-write"/> 
        <id name="addressId" type="long">
            <column name="ADDRESS_ID" precision="22" scale="0" />
            <generator class="increment" />
        </id>
        <property name="street" type="string">
            <column name="STREET" length="50" />
        </property>
        <property name="city" type="string">
            <column name="CITY" length="20" />
        </property>
        <set name="usrs" inverse="true" cascade="all-delete-orphan">
            <key>
                <column name="ADDRESS_ID" precision="22" scale="0" not-null="true"/>
            </key>
            <one-to-many class="Usr" />
        </set>
    </class>


</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
    Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<hibernate-mapping>
    <class name="Usr" table="USR" >
        <cache usage="read-write"/>
        <id name="usrId" type="long">
            <column name="USR_ID" precision="22" scale="0" />
            <generator class="increment" />
        </id>
        <many-to-one name="address" class="Address" >
            <column name="ADDRESS_ID" precision="22" scale="0"  />
        </many-to-one>
        <property name="logname" type="string">
            <column name="LOGNAME" length="20" not-null="true" />
        </property>
        <property name="password" type="string">
            <column name="PASSWORD" length="20" not-null="true" />
        </property>
    </class>

   <query name="Usr.by.city">
        <![CDATA[
           FROM rUsr as u          
           WHERE  u.address.city = :city 
        ]]>
    </query>
</hibernate-mapping>

If I set lazy=false I get an error on deletion :
deleted object would be re-saved by cascade

and I set lazy=true then I won’t be able to access my objects due to lazy initialization errors.

Any help is appreciated.

Thx.

Answer 1

You need to remove Usr from the corresponding Address.usrs before removing it from the database. Otherwise Hibernate tries to re-save it by cascading, since usrs is configured as cascade="all-delete-orphan".

With lazy = "true" you don’t have this problem since cascading is not applied to uninitialized lazy collections.

Also, declaring all relationships as eager is not always a good solution for lazy initialization problems. Other possible solutions include Open Session in View pattern and fine-grained fetch strategy tuning with join fetch and so on.