inheritance mapping

diegdocr · **Joined:** Mon Jan 09, 2006 1:32 am **Posts:** 3

Hello, Is it possible to map an entire inheritance hirachy?

for example:
Person -> User -> UserT //this are the classes whose objs need.
_____________-> UserC
______-> Contact

But for mapping this i should start from person class.
Is It possible to do this...
<class>
.......
<discriminator column="person_t"/>
<subclass name="User" discriminator-value="USER">
<discriminator column="user_type"/>
............
<subclass name="" dicriminator-value="USERT" />
<subclass name="" dicriminator-value="USERC" />
</subclass>
<subclass name="Contact" discriminator-value="CONTACT"/>
</class>

This is a 3 level example, could be more, but all the tutorials, docs, and books i been read, only shows 2 level inheritance. I thought that with nesting subclasses could be done the job.

But, if is immposible, i was thinking maybe if i start the mapping from de second level, from user, but Do i have to override the properties, methods, from Person?, or Hibernate take the inheritance, extends Person (take all from here)

zzyborg · **Posted:** Wed Jan 11, 2006 4:33 am

as far as i know you can have nested <subclass >
correct me if i am wrong

rdonasco · **Joined:** Wed Jan 11, 2006 5:21 am **Posts:** 14

Yes it is possible. Please read the following example mapping.

Code:

        <class name="poc.user.model.User" 
            table="USER" lazy="false" discriminator-value="USER">
                <id name="userID" type="string" length="20"/>
                <discriminator column="subclass" type="string"/>
                <property name="birthday"      type="date"/>
                <property name="firstname"     type="string" length="20" not-null="true"/>
                <property name="lastname"      type="string" length="20" not-null="true"/>
                <property name="middlename"    type="string" length="20"/>
                <property name="image"         type="binary" length="2048000"/>
                <component
                    name="homeAddress"
                    class="poc.user.model.Address">
                    <property name="street" column="homeStreet" type="string" length="100" not-null="true"/>
                    <property name="city" column="homeCity" type="string" length="30" not-null="true"/>
                    <property name="state" column="homeState" type="string" length="30"/>
                    <property name="zip" column="homeZip" type="string" length="10"/>
                    <property name="country" column="homeCountry" type="string" length="2" not-null="true"/>
                </component>
                
                <list
                    name="roles"
                    table="userRoles"
                    lazy="false">
                    <key column="userID" not-null="true"/>
                    <list-index column="roleIndex"/>
                    <composite-element class="poc.user.model.Role">
                        <property name="name" length="10"/>
                        <property name="description"/>
                    </composite-element>
                </list>
                
                <subclass name="poc.user.model.Admin"
                    discriminator-value="Admin">
                        <property name="equipment" type="string"/>
                        <subclass name="poc.user.model.Manager"
                            discriminator-value="Manager">
                            <property name="car" type="string"/>
                        </subclass>
               </subclass>
                
        </class>

In this mapping I defined subclass hierarchy User->Admin->Manager

The only thing you should notice is that it only creates one table "User". It will contain all the columns from User, Admin, and Manager objects.

Kind regards,
Roy