@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@Table(name = "sf_persistent_object")
abstract class PersistentObject implements Serializable
{
   private static final long serialVersionUID = -3555198930641746803L;

   private long id;
   private Calendar lastModifiedDate;
   private Calendar creationDate;
   private Account lastChanger;
   private Account creator;

   @Id(generate = GeneratorType.TABLE, generator = "obj_id_gen")
   @Column(name = "id")
   public long getId()
   {
      return id;
   }

   @Column(name = "last_modified_date", nullable = false)
   public Calendar getLastModifiedDate()
   {
      return lastModifiedDate;
   }

   @Column(name = "creation_date", nullable = false)
   public Calendar getCreationDate()
   {
      return creationDate;
   }

   @ManyToOne(cascade = CascadeType.ALL)
   @JoinColumn(name = "fk_last_changer_id", nullable = false)
   public Account getLastChanger()
   {
      return lastChanger;
   }

   @ManyToOne(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
   @JoinColumn(name = "fk_creator_id", nullable = false)
   public Account getCreator()
   {
      return creator;
   }

   public void setId(long id)
   {
      this.id = id;
   }

   public void setLastModifiedDate(Calendar lastModified)
   {
      this.lastModifiedDate = lastModified;
   }

   public void setCreationDate(Calendar creationDate)
   {
      this.creationDate = creationDate;
   }

   public void setCreator(Account owner)
   {
      this.creator = owner;
   }

   public void setLastChanger(Account lastChanger)
   {
      this.lastChanger = lastChanger;
   }

}

@Entity(access = AccessType.PROPERTY)
@PrimaryKeyJoinColumn(name="fk_persistent_object_id")
@Table(name = "sf_account")
@TableGenerator(name = "obj_id_gen", tableName = "GEN_TABLE", pkColumnValue = "global_object_id", allocationSize = 1)
@GeneratedIdTable(
   name="GEN_TABLE",
   table = @Table(name="sf_hibernate_sequences")
)
public class Account extends PersistentObject
{
   private static final long serialVersionUID = -9009838260646199450L;
   
   private String username;
   private String password;
   private String email;
   
   public Account()
   {
      super();
   }
   
   public Account(String email, String password)
   {
      this.email = email;
      this.password = password;
   }

   @Basic
   @Column(name = "email")
   public String getEmail()
   {
      return email;
   }
   public void setEmail(String email)
   {
      this.email = email;
   }
   @Basic
   @Column(name = "username")
   public String getUsername()
   {
      return username;
   }

   public void setUsername(String username)
   {
      this.username = username;
   }
   @Basic
   @Column(name="password")
   public String getPassword()
   {
      return password;
   }
   public void setPassword(String password)
   {
      this.password = password;
   }
}