Using multiple lists in Hibernate

Question

I have a Person class mapped to a PERSON table, and an Address class mapped to an ADDRESS table. What I want is for each Person to have two lists of Addresses: homeAddresses and officeAddresses. The ADDRESS table has one foreign-key field, PERSONID, for both cases, but it has two separate list-index fields: a home_add_idx for records belonging in homeAddresses, and an off_add_idx for records belonging in officeAddresses. For any given ADDRESS record, one of these list-index fields will be NULL. This all works perfectly on insert, but when I try to retrieve records, I get an exception, "null index column for collection". (Full stacktrace below.)

How can I do this?

Person.java:

public class Person implements Serializable {
    private String personId;
    private String personName;
    private List<Address> homeAddresses = new ArrayList<Address>();
    private List<Address> officeAddresses = new ArrayList<Address>();

    public String getPersonId() { return personId; }
    public void setPersonId(String s) { personId = s; }
    public String getPersonName() { return personName; }
    public void setPersonName(String s) { personName = s; }
    public List<Address> getHomeAddresses() { return homeAddresses; }
    public void setHomeAddresses(List<Address> L) { homeAddresses = L; }
    public List<Address> getOfficeAddresses() { return officeAddresses; }
    public void setOfficeAddresses(List<Address> L) { officeAddresses = L; }
}

Address.java:

public class Address implements Serializable {
    private String id;
    private String houseNo;
    // [SNIP - street, city, country]
    private String postalCode;

    public String getId() { return id; }
    public void setId(String s) { id = s; }
    public String getHouseNo() { return houseNo; }
    public void setHouseNo(String s) { houseNo = s; }
    // [SNIP - getters for street, city, country]
    public String getPostalCode() { return postalCode; }
    public void setPostalCode(String s) { postalCode = s; }
}

Person.hbm.xml:

<hibernate-mapping>
<class name="com.nadhi.list.test.Person" table="PERSON">
    <id name="personId" type="java.lang.String">
        <column name="PERSONID" />
        <generator class="assigned" />
    </id>
    <property name="personName" type="java.lang.String">
        <column name="PERSONNAME" />
    </property>
    <list name="homeAddresses" inverse="false" table="ADDRESS" lazy="false" cascade="all">
        <key>
            <column name="PERSONID"/>
        </key>
       <list-index column="home_add_idx"></list-index>
        <one-to-many class="com.nadhi.list.test.Address" />
    </list>
    <list name="officeAddresses" inverse="false" table="ADDRESS" lazy="false" cascade="all">
        <key>
            <column name="PERSONID"/>
        </key>
       <list-index column="off_add_idx"></list-index>
        <one-to-many class="com.nadhi.list.test.Address" />
    </list>
</class>
</hibernate-mapping>

Address.hbm.xml:

<hibernate-mapping>
<class name="com.nadhi.list.test.Address" table="ADDRESS">
    <id name="id" type="java.lang.String">
        <column name="ID" />
        <generator class="assigned" />
    </id>
    <property name="houseNo" type="java.lang.String">
        <column name="HOUSENO" />
    </property>
    <!-- [SNIP - mappings for street, city, country] -->
    <property name="postalCode" type="java.lang.String">
        <column name="POSTALCODE" />
    </property>
</class>
</hibernate-mapping>

When I insert data, I insert a separate home and office address for the same Person. It inserts correctly. However, when I try to retrieve the Person object, I get the following exception:

org.hibernate.HibernateException: null index column for collection: com.nadhi.list.test.Person.officeAddresses
at org.hibernate.persister.collection.AbstractCollectionPersister.readIndex(AbstractCollectionPersister.java:770)
at org.hibernate.collection.PersistentList.readFrom(PersistentList.java:402)
at org.hibernate.loader.Loader.readCollectionElement(Loader.java:1156)
at org.hibernate.loader.Loader.readCollectionElements(Loader.java:774)
at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:622)
at org.hibernate.loader.Loader.doQuery(Loader.java:829)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:274)
at org.hibernate.loader.Loader.loadCollection(Loader.java:2166)
at org.hibernate.loader.collection.CollectionLoader.initialize(CollectionLoader.java:62)
at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:627)
at org.hibernate.event.def.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:83)
at org.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:1863)
at org.hibernate.collection.AbstractPersistentCollection.forceInitialization(AbstractPersistentCollection.java:479)
at org.hibernate.engine.StatefulPersistenceContext.initializeNonLazyCollections(StatefulPersistenceContext.java:900)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:279)
at org.hibernate.loader.Loader.doList(Loader.java:2533)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2276)
at org.hibernate.loader.Loader.list(Loader.java:2271)
at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:119)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1716)
at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:347)
at org.hibernate.impl.CriteriaImpl.uniqueResult(CriteriaImpl.java:369)
at com.nadhi.list.test.Main.getPerson(Main.java:113)
at com.nadhi.list.test.Main.main(Main.java:36)

In the database, I can see that for home address, the office address column index is empty; and for office address, the home address column index is empty. But isn't that expected? What do I need to do in order to retrieve the data correctly?

Answer 1

I think you need to replace the ADDRESS.PERSONID foreign-key field with two separate foreign-key fields — one for home addresses, one for office addresses.

The list-index fields, you can leave as they are, or you can merge them into a single field, or you can remove them entirely and use a <bag> instead of a <list> mapping. (Obviously that last approach is only good if you don't care about the order of addresses within the list; I don't know whether you do.)

When you think about it — it makes sense that the list-index column doesn't accomplish what you want. That column is only used for lists (not sets and bags), so it would not be a very general-purpose way to indicate which collection a record belongs to. So it makes sense that it's only used to specify the list-index for a record that's already been determined to belong to the right collection.