Hi,

I am using Hibernate version 3.

I am trying to map a single class "Animal" into 2 tables "ExtinctAnimals" and "NonExtinctAnimals" depending on the value of the "extinct" property. If the object has a value of "true" for the extinct property, then it should be stored into the "ExtinctAnimals" table. If it has a value of "false", then it should be stored in the "NonExtinctAnimals" table.

The same should also occur while loading the object. So, it the object is loaded from the "ExtinctAnimals" table, it should automatically set the value of the "extinct" property to true.

I would like to know what kind of mappings to use for the same. I tried the following :



But, Hibernate complains that the classes "ExtinctAnimals" and "NonExtinctAnimals" do not exist. Attached at the bottom is the stack trace.

What would be a good mapping for my problem?
Or are there better recommended ways of doing things?

Thanks in advance.



Java Exception :
Caused by: java.lang.ClassNotFoundException: ExtinctAnimals
at java.net.URLClassLoader.findClass(URLClassLoader.java:376)
at java.lang.ClassLoader.loadClass(ClassLoader.java:570)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:442)
at java.lang.ClassLoader.loadClass(ClassLoader.java:502)
at java.lang.Class.forName1(Native Method)
at java.lang.Class.forName(Class.java:180)
at org.hibernate.util.ReflectHelper.classForName(ReflectHelper.java:108)
at org.hibernate.util.ReflectHelper.reflectedPropertyClass(ReflectHelper.java:76)

Hi Spaceman,

With the use a discriminator, your ExtinctAnimals and NonExtinctAnimals will end up in one table:

<class name="Animal" table="Animal">
<discriminator column="extinct" />
... // declaration of properties
<subclass name="NonExtinctAnimal" discriminator-value="false">
...
</subclass>
<subclass name="ExtinctAnimal" discriminator-value="true">
...
</subclass>
</class>


but then you will have to create the subclasses NonExtinctAnimal and ExtinctAnimal.

I know it is a bit turned around, with only one table and 2 subclasses, but I think it could work for you, or is it a requirement that the animals are stored in 2 tables?

Hope to have helped,

DrAvanlch.

Hi drAvaInch,

Thanks for your quick reply!

But, unfortunately, it is a requirement to use just 1 class and 2 tables. I am a Java-Hibernate programmer and I cannot mess with the DB Schema.

Hibernate easily maps 2 subclasses to 1 table, but I wasnt able to do it the other way round using a discriminator.

Thanks,

Spaceman

Hi Spaceman,

Ok.
Let me just think that over for a few moments... :-)

Hope to get back to you,

DrAvalnch.

Hi Spaceman,

This might get you on the way (using the entity-name) :

<class name="Animal" table="ExtinctAnimals" proxy="Animal" entity-name="ExtinctedAnimals" >
...
</class>
<class name="Animal" table="NonExtinctAnimals" proxy="Animal" entity-name="NonExtinctedAnimals" >
...
</class>

But I'm not really sure how to put in the discriminator.

But since you are the Java-Hibernate programmer you can decide on the classes, no?

You then could do something like :

abstract class Animal {

}

class ExtinctAnimal extends Animal{
...
}

class NonExtinctAnimal extends Animal {
...
}

<class name="Animal" >
<id name="id" type="long" column="ANIMAL_ID">
<generator class="sequence"/>
</id> ...
<union-subclass name="ExtinctAnimal" table="ExtinctAnimal">
...
</union-subclass>
<union-subclass name="NonExtinctAnimal" table="NonExtinctAnimal">
...
</union-subclass>
</class>

Both tables should have the ANIMAL_ID as key.

Hope to have helped,

DrAvalnch.