Hibernate exception while saving with cascade=“save-update”

Question

Here is my hbm and test code respectively. I am using Spring\'s HibernateTemplate. I doesn\'t use DAO. Hibernate 2.2.5 with Spring 2.0.7

hbm

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Answer 1

since instances of the same class are both parents and children, you need an id, which you have, but you also need a parent-id type column in the db (and field on the class) so the children can have a reference to their parent.

See https://forum.hibernate.org/viewtopic.php?f=1&t=1004163

Answer 2

Ok the root cause was the invalid mapping on my part for the collection. Thanks to this article on composite mapping

Wrong:

<key>
  <column name="ID" />
</key>

Correct

<many-to-one name="parent" class="Product" lazy="false" column="PARENT" />

<set name="children" lazy="false" fetch="join" table="PRODUCT" cascade="all">
  <key>
    <column name="PARENT" />
  </key>
  <one-to-many class="Product" />
</set>

Complete mapping

<class name="Product" table="PRODUCT">
        <id name="id" type="java.lang.Long" column="ID">
            <generator class="native">
                <param name="sequence">PRODUCT_SN</param>
            </generator>
        </id>

        <many-to-one name="parent" class="Product" lazy="false" column="PARENT" />

        <set name="children" lazy="false" fetch="join" table="PRODUCT" cascade="all">
            <key>
                <column name="PARENT" />
            </key>
            <one-to-many class="Product" />
        </set>
        <property name="code" type="java.lang.String" column="CODE" not-null="true" />
        <property name="name" type="java.lang.String" column="NAME" />
        <property name="startDate" type="java.util.Date" column="STARTDATE" />
        <property name="endDate" type="java.util.Date" column="ENDDATE" />
        <property name="decisionable" type="boolean" column="ISDECISIONABLE" />
        <property name="selectable" type="boolean" column="ISSELECTABLE" />
    </class>

Answer 3

When you made a bidirectional relationship you need to put inverse=true otherwise hibernate is going to try to do a double access and that is why you are getting a exception. Hibernate needs to know which side of the relationship is the one who has the control of saving and updating.