Null Collections

edalquist · **Joined:** Thu Oct 06, 2005 7:34 pm **Posts:** 20

Is there a way to get a collection mapped in hibernate to load a null value instead of an empty collection if there is no data for the collection in the database?

From the example below there is no data for the keywords list. I would like the PortletInfoImpl created by hibernate to set null for the keywords property instead of an empty list as they have two different meanings for this application.

Hibernate version: 3.2.0-ga

Mapping documents:

Code:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping default-lazy="false">
    <class name="org.jasig.portal.portlet.transfer.impl.PortletDefinitionTransferImpl"
        table="UP_PORT_DEF">
        
        <id name="portletDefinitionId" type="org.jasig.portal.portlet.dao.hibernate.types.PortletDefinitionIdUserType">
            <column name="PORT_DEF_ID"/>
            <generator class="assigned"/>
        </id>
        <component name="portletInfo" class="org.jasig.portal.portlet.common.PortletInfoImpl">
            <property name="title" type="string">
                <column name="INFO_TITLE"/>
            </property>
            <property name="shortTitle" type="string">
                <column name="INFO_SHORT_TITLE"/>
            </property>
            <list name="keywords" table="UP_PORT_DEF_INFO_KEYWORDS" cascade="all">
                <key>
                    <column name="PORT_DEF_ID"/>
                </key>
                <index column="SORT_ORDER"/>
                <element type="string">
                    <column name="KEYWORD" not-null="true"/>
                </element>              
            </list>
        </component>
    </class>
</hibernate-mapping>

Name and version of the database you are using: HSQL 1.8.0.2

kochcp · **Posted:** Thu Feb 15, 2007 3:37 pm

can you just extend the POJO, overwrite the getter, and return null if it's empty

edalquist · **Joined:** Thu Oct 06, 2005 7:34 pm **Posts:** 20

If I do that hibernate complains when populating a List with content since its operation is to set an empty PersistentList then get it each time it adds an item. The first get will always return null which is a problem.

kochcp · **Posted:** Thu Feb 15, 2007 4:18 pm

True. Well I'm not sure there is a way to have hibernate do what you want to.

sebas · **Joined:** Wed Aug 24, 2005 1:43 pm **Posts:** 10

what you could do is have two get methods:

protected List children = new ArrayList();

public List getChildren()
{
if (children.size() == 0) return null;
return children;
}

protected List getChildrenHib()
{
return children;
}

protected void setChildrenHib(List children)
{
this.children = children;
}

The protected methods are just for hibernate purposes, so you'd use childrenHib in your mapping files, and your client code can use the public one.

Cheers!
Seb

max · **Posted:** Fri Feb 16, 2007 5:45 am

first of all null and isEmpty() is NOT the same - why would you ever want to make that the same ?

Anyhow, no need for tricks like getXXXHib() methods - just use access="field"