Component of Components

Hibernate allows us to compose our components out of other components. This is making extreme use of java in the SQL world, but provides us with a great deal of flexibility. I modified the address class in the previous example to be composed of components.
So the address class now looks like

public class Address {
    private Person person;
    private String city;
    private Location location;
    private ZipCode zipCode;
        //setter-getters 

}

The components placed inside Address class are as follows:

public class Location {
    private Street street;
        //setter-getters
}

public class Street {
    private String name;
        //setter-getters
}

public class ZipCode {
    private String zipCode;
        //setter-getters
}

The database table is unchanged.However the mapping file is modified to the following:

<?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 package="com.model.components.bidirectional">
    <class name="Person" table="PERSON">
        <id name="id" type="long">
            <column name="ID" />
            <generator class="native" />
        </id>
        <property name="name" type="string">
            <column name="NAME" />
        </property>

        <component name="address" class="ComponentAddress">
            <parent name="person" />
            
            <property name="city" type="string" not-null="true">
                <column name="CITY" />
            </property>
            <component name="location" class="Location">
                <component name="street" class="Street">

                    <parent name="person" /> 
                    <property name="name" type="string" not-null="true">
                        <column name="STREET" />
                    </property>
                </component>
            </component>
            
            <component name="zipCode" class="ZipCode">    
                <property name="zipCode" type="string" not-null="true">
                    <column name="ZIP_CODE" />
                </property>
            </component>
        </component>
    </class>
</hibernate-mapping>

I have highlighted the component nesting levels in the code above. As can be seen the back-link is not only present for the outer-most component but also for inner component Location. Backlinks always refer to the entity and not the class that includes the component instance !!
I decided to execute an HQL query to retrieve a Person object for a given Street name

static void testHqlRetrieval() {
    Session session = SESSION_FACTORY.openSession();
    try {
        //get Entity with query on component
        Query query = session.createQuery("from Person p where p.address.location.street.name = ?");
        query.setString(0, "Aundh Road");
        Person person = (Person) query.list().get(0);
        System.out.println("Person : " + person + " City : " 

              + person.getAddress().getCity());
        System.out.println("Inner person back -reference " 

              + person.getAddress().getLocation().getStreet().getPerson().getName());
    } catch (HibernateException e) {
        e.printStackTrace();
    } finally {
        session.close();
    }
}

The code for back-reference is crooked to say the least, but it works ;P The logs indicate the SQL query fired

3016 [main] DEBUG org.hibernate.SQL  -  
    select
        person0_.ID as ID0_,
        person0_.NAME as NAME0_,
        person0_.CITY as CITY0_,
        person0_.STREET as STREET0_,
        person0_.ZIP_CODE as ZIP5_0_ 
    from
        PERSON person0_ 
    where
        person0_.STREET=?