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Mapping a composite pattern (without a parent)

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FesterWim

Post subject: Mapping a composite pattern (without a parent)

Posted: Wed Oct 15, 2008 5:00 am

Newbie

Joined: Tue Jan 06, 2004 5:52 am
Posts: 17
Location: Belgium

Hi,

I am trying to map a composite pattern based hierarchy. I have the following classes:

* Interface 'Filter'
* Class 'CombinedFilter' containing a List<Filter>
* Class 'AbstractSingleFilter'
* Some implementation classes that subclass AbstractSingleFilter

I am using Hibernate Annotations 3.4.0. I already found out that you cannot use annotations and interfaces, so I created a hbm.xml file for my interface

Code:

<hibernate-mapping>
    <class name="com.mycomp.domain.filter.Filter">
        <id name="id"/>
    </class>
</hibernate-mapping>

The combined filter class is mapped like this:

Code:

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public class CombinedFilter implements Filter
{

   @Id
   @Column(name = "Id")
   private Long m_id;

   @Column(name = "ChildFilters")
   private List<Filter> m_filters;

   @Column(name = "CombinationType")
   private CombinationType m_combinationType;

   @Column(name = "Name")
   private String m_name;

This the AbstractSingleFilter:

Code:

@MappedSuperclass
@Inheritance(strategy = InheritanceType.JOINED)
public abstract class AbstractSingleFilter implements Filter
{

   @Id
   @Column(name = "Id")
   private Long m_id;

   @Column(name = "Name")
   private String m_name;

And this is a concrete implementation:

Code:

@Entity
@PrimaryKeyJoinColumn(name="AbstractSingleFilterId")
public class ZoneIdFilter extends AbstractSingleFilter
{
   @Column(name = "ZoneId")
   private int m_zoneId;

What do I need to annotate the m_filters variable in CombinedFilter with to make this work?

I found this example but it has a slightly different hierarchy. It does not use an interface and it has a link back to the parent, which I don't have here.

regards,

Wim

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FesterWim

Post subject:

Posted: Wed Oct 15, 2008 5:23 am

Newbie

Joined: Tue Jan 06, 2004 5:52 am
Posts: 17
Location: Belgium

I found out that if I use this:

Code:

   @Column(name = "ChildFilters")
   @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
   @JoinColumn(name = "ParentFilterId")
   private List<Filter> m_filters;

Then I get 4 tables generated and the CombinedFilter and Filter tables are correctly filled up. However, the tables with the concrete types are still empty. I am using session.saveOrUpdate() with a CombinedFilter object containing 2 AbstractSingleFilter subclasses.

Any idea why the cascading does not work?

regards,

Wim
Update:
I switched to a join table (As recommended in the documentation: "A unidirectional one to many with join table is much preferred")

But this makes no difference. This is the sql that is generated:

Code:

Hibernate: select combinedfi_.Id, combinedfi_.CombinationType as Combinat2_3_, combinedfi_.Name as Name3_ from CombinedFilter combinedfi_ where combinedfi_.Id=?
Hibernate: select filter_.id from Filter filter_ where filter_.id=?
Hibernate: select filter_.id from Filter filter_ where filter_.id=?
Hibernate: insert into CombinedFilter (CombinationType, Name, Id) values (?, ?, ?)
Hibernate: insert into Filter (id) values (?)
Hibernate: insert into Filter (id) values (?)
Hibernate: insert into ChildFilters (ParentFilterId, ChildFilterId) values (?, ?)
Hibernate: insert into ChildFilters (ParentFilterId, ChildFilterId) values (?, ?)

What hibernate should do is see that the child filters are of a certain subclass and update those tables also, and not only insert records in the Filter table.

regards,

Wim

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