Hibernate version:3.0


How do I persist the subclass of a class using table-per-subclass mapping?
Using hibernate, I created the following tables and mappings.

I inserted the following data into the events table:
(1, “Filmshow”, 5)

I tried to do the following but it failed with the following error:
not-null property references a null or transient value: Event.name;

public class Main {

public Main() {
super();
}

public static void main(String[] args) {
Configuration cfg = new Configuration()
.addClass(NetworkingEvent.class)
.setProperty("hibernate.dialect", org.hibernate.dialect.MySQLInnoDBDialect")
.setProperty("hibernate.connection.driver_class", "com.mysql.jdbc.Driver")
.setProperty("hibernate.connection.url", "jdbc:mysql://localhost/javalobby")
.setProperty("hibernate.connection.username", "admin");

SessionFactory sessions = cfg.buildSessionFactory();

Session session = sessions.openSession();
try {
NetworkingEvent netEvent = new NetworkingEvent();
netEvent.setId(1);
netEvent.setNumSeats(5);
session.saveOrUpdate(netEvent);
System.out.println(user);
}
finally {
session.close();
}

}
}

The parent class:
----------------------------------
/**
* @hibernate.class
* table="event "
*/
public class Event implements Serializable {
private long id;
private String name;
Private int duration;
public Event () {
}
/**
* @hibernate.id
* generator-class="assigned"
* type="long"
* column="id"
*/
public long getId() {
return id;
}
public void setId(long theId) {
id = theId;
}
/**
* @hibernate.property length="50" not-null="true" unique="true"
*/
public String getName() {
return name;
}
public void setName(String name) {
name = name;
}

//Other properties
}
----------------------------------
The child class:
----------------------------------
import java.io.Serializable;
/**
* @hibernate.joined-subclass
* table="net_Events"
*
* @hibernate.joined-subclass-key
* column="id"
*/
public class NetworkingEvent extends Event implements Serializable {
private int numSeats;
/** default constructor */
public NetworkingEvent() {
super();
}
/**
* @hibernate.property
* column="num_seats"
*/
public int getNumSeats() {
return numSeats;
}
public void setNumSeats (int numSeats) {
numSeats = numSeats;
}
}

The Event.hbm.xml file:
----------------------------------
<class name="Event" table="events">
<id name="id" type="long">
<generator class="native"/>
</id>
<joined-subclass name="NetworkingEvent" table="net_events">
<key column="id"/>
...
</joined-subclass>
</class>


Full stack trace of any exception that occurs:
not-null property references a null or transient value: Event.name;

The error said exactly what the problem really was:

versus
not-null property references a null or transient value: Event.name; means that property name of class Event should not be null, but it is.

That was what I thought too.

But on calling setName() there was another error of "Duplicate entry for key".