hibernate sequence generator

ru.olimpiks.MySequenceGenerator.java

public class MySequenceGenerator implements IdentifierGenerator {
  public static final String QUERY_NAME = "MySequence.newId";

  public Serializable generate(SessionImplementor session, Object object)
      throws HibernateException {

    Long id = null;
    Connection connection = session.connection();

    try {
      PreparedStatement preparedStatement = connection.prepareStatement(session
          .getNamedQuery(QUERY_NAME).getQueryString());

      ResultSet resultSet = preparedStatement.executeQuery();
      if (resultSet.next()) {
        id = resultSet.getLong(1);
      }
    } catch (SQLException e) {
      e.printStackTrace();
    }
    return id;
  }
}

hbm.xml

...
<sql-query name="MySequence.newId">
 <return-scalar column="id" type="long" />
 <![CDATA[
  select
   seq_my.NEXTVAL id
  from
   dual
 ]]>
</sql-query>
...

ru.olimpiks.MyEntity.java

@Entity
@Table(name = "MY_TABLE")
public class MyEntity implements java.io.Serializable {

  private Long id;

  @Id
  @Column(name = "ID")
  @GeneratedValue(generator = "my_id")
  @GenericGenerator(name = "my_id", strategy = "ru.olimpiks.MySequenceGenerator")
  public Long getId() {
    return this.id;
  }

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