Hibernate version: 3.1 beta 1
Hibernate annotations version: 3.1 beta 4
Name and version of the database you are using: MySQL 4.1.13

I have an abstract class User which is extended by the three classes Student, Lecturer and Administrator using the strategy single table per class hierarchy.

When trying to get it started, I get the exception below. I could not figure out what I went wrong. Maybe it's just too late... 8)
I hope you can help me. Thanks in advance!

User:
@Entity()
@org.hibernate.annotations.Entity(dynamicUpdate = true)
@Table(name = "users")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE, discriminatorType = DiscriminatorType.STRING)
@DiscriminatorColumn(name = "discriminator")
public abstract class User implements Comparable {
...
}

Student:
@Entity()
@org.hibernate.annotations.Entity(dynamicUpdate = true)
@Inheritance(discriminatorValue = "student")
public class Student extends User {
...
}

Lecturer:
@Entity()
@org.hibernate.annotations.Entity(dynamicUpdate = true)
@Inheritance(discriminatorValue = "lecturer")
public class Lecturer extends User {
...
}

Administrator:
@Entity()
@org.hibernate.annotations.Entity(dynamicUpdate = true)
@Inheritance(discriminatorValue = "administrator")
public class Administrator extends User {
...
}

Full stack trace of any exception that occurs:

Well, I think it was really to late. :)
I just forgot to map the derived classes in the hibernate.cfg.xml.

<mapping class="de.w3s.persistence.Student"/>
<mapping class="de.w3s.persistence.Lecturer"/>
<mapping class="de.w3s.persistence.Administrator"/>

Best regards
Sven

You can use the .par feature of Hibernate entity Manager to avoid this kind of mistake in the future.
http://blog.hibernate.org/cgi-bin/blosxom.cgi/2005/08/04#par-archive