title: Hibernate not inserting DTYPE - value is null
body: <p>I have essentially the following classes:</p>
  
  <pre><code>@Entity
  @Table( name="user" )
  @Inheritance( strategy = InheritanceType.JOINED )
  public abstract class User implements Serializable
  {
    private static final long serialVersionUID = 1L;
  
    @Id
    @GeneratedValue( strategy = GenerationType.IDENTITY )
    @Column( name = "id" )
    private Long id;
  
    @Column( name = "email_address" )
    private String emailAddress;
  
    /* getters and setters not shown */
  }
  </code></pre>
  
  <p>and </p>
  
  <pre><code>@Entity
  @Table( name="admin" )
  public class Admin extends User implements Serializable
  {
    private static final long serialVersionUID = 1L;
  
    @Column( name = "role" )
    private String role;
  
    /* getters and setters not shown */
  }
  </code></pre>
  
  <p>I expect Hibernate to use by default a column <code>DTYPE varchar(31)</code> which exists in the <code>user</code> table. When my code tries to persist a new Admin object I see the following logged to console:</p>
  
  <pre><code>Hibernate: insert into user (email_address) values (?)
  Hibernate: insert into admin (role) values (?) 
  </code></pre>
  
  <p>Thus no attempt is made by Hibernate to set the <code>user.DTYPE</code> column, and it remains NULL in the database. I expected it would be set to <code>Admin</code>.</p>
  
  <p>What am I doing wrong? I have also tried explicitly setting <code>@DiscriminatorColumn</code> on the User class and <code>@DiscriminatorValue</code> on the <code>Admin</code> class (and also tried adding to User as well) but to no avail.</p>