Recursive Elements in Table -> PropertyValueException

FriedDust · **Posted:** Thu Jul 26, 2007 5:35 am

im pretty new with Hibernate..
I have a table named accountHeadGroups

Code:

id   parentId  code   name
1     0            a        abc
2     0            b        bmn
3     1            c        fffff
4     3            d        gggg

(abc(root) -> fffff (child) -> gggg (child))
if the parentId is zero then it is the root element.

Code:

<hibernate-mapping>
  <class name="pojo.AccountHeadGroup" table="accountHeadGroups">
   <id name="id" type="int" column="id" >
   <generator class="increment"/>
  </id>

  <set name="children" inverse="true" cascade="all-delete-orphan" lazy="true" order-by="id" >
    <key column="parentId" not-null="true" />
    <one-to-many class="pojo.AccountHeadGroup" />
    </set>

    <many-to-one name="parent"
          column="parentId"
          class="pojo.AccountHeadGroup"          
          not-null="true"
          insert="true"
          update="true"
          lazy="false"
          not-found="ignore"
    />

  <property name="code">
    <column name="code"/>
  </property>
  <property name="name">
    <column name="name"/>
  </property>
 </class>
</hibernate-mapping>

Now, if I want to add a new AccountHeadGroup then
AccountHeadGroup ahg = new AccountHeadGroup();
ahg.setParent(someParent);
ahg.setCode("c");
ahg.setName("name");
session.save(ahg); and it'll work fine

but when I want to add/edit an AccountHeadGroup myGroup, whose parentId is 0 (root element), then myGroup's parent would be null.. and if I try to saveOrUpdate myGroup, it will throw org.hibernate.PropertyValueException: not-null property references a null or transient value: pojo.ItemGroup.parent

any advice????

thatmikewilliams · **Posted:** Thu Jul 26, 2007 8:17 am

You've specified in the mapping file that the parent is not-null="true". However, you _are_ expecting the parent entity to be null in some circumstances so the mapping doesn't match what will happen in the java.

- try setting not-null="false"

Mike

FriedDust · **Posted:** Thu Jul 26, 2007 8:26 am

setting it to not-null false will set the parentId NULL in the database, which is not what I want.
actually, i want the parentId to be 0 if there is no parentGroup (parentId 0 means it is in the first level)

thatmikewilliams · **Posted:** Thu Jul 26, 2007 8:58 am

I don't think you can force the value to be set to 0 when the parent is null. Why do you need 0 rather than null anyway? This seems a little unusual.

ipso.facto · **Posted:** Thu Jul 26, 2007 10:28 am

You can just create a node that 'represents' null, i.e.:

Code:

id   parentId  code   name
0     0            null     null
1     0            a        abc
2     0            b        bmn
3     1            c        fffff
4     3            d        gggg

That way no node, including the "null node," actually has a null value as the parent.

FriedDust · **Posted:** Thu Jul 26, 2007 10:35 am

good idea, but then I have to modify all my codes as "from accountHeadGroups a WHERE a.id > 0" :-(

I think I should go back to my good old JDBC days! ;)

ipso.facto · **Posted:** Thu Jul 26, 2007 10:50 am

Instead of modifying the HQL query you could just apply a filter that would work just the same but with less code rewrite.