@TableGenerator(name="doc-generator", table="ids", pkColumnValue="seq_doc_generator", allocationSize=0x10)
// таблица-заглушка
@Entity
@Table(name="dummy_doc")
public class DummyDoc {
	private Long id;
	@Id
	@GeneratedValue(strategy=GenerationType.TABLE, generator="doc-generator")
	public Long getId() {
		return id;
	}
	public void setId(Long id) {
		this.id = id;
	}
}

/// и где-то в коде
	public Long nextId() {
		SessionFactoryImplementor sfi = (SessionFactoryImplementor)sessionFactory;
		IdentifierGenerator generator = sfi.getIdentifierGenerator(DummyDoc.class.getName());
		Session session = sessionFactory.getCurrentSession();
		Long value = (Long)generator.generate((SessionImplementor)session, null);
		return value;
	}

<prop key="hibernate.hbm2ddl.auto">update</prop>

		SessionFactoryImplementor sfi = (SessionFactoryImplementor)sessionFactory;
		IdentifierGeneratorFactory igf = sfi.getIdentifierGeneratorFactory();
		igf.createIdentifierGenerator(strategy, type, config)

// класс заглушка
@GenericGenerator(
		name = "doc_generator",
		strategy = "org.hibernate.id.enhanced.TableGenerator",
		parameters = {
				@Parameter(name = "segment_value", value = "seq_doc_generator"),
				@Parameter(name = "increment_size", value = "64"),
		})
@Entity 
@Subselect("")
public class DummyDoc {
	@Id @GeneratedValue(generator="doc_generator")
	private Long id;
}
// получение уникального значения
	@Transactional
	public Long nextId() {
		SessionFactoryImplementor sfi = (SessionFactoryImplementor)sessionFactory;
		IdentifierGenerator generator = sfi.getIdentifierGenerator(DummyDoc.class.getName());
		Session session = sessionFactory.getCurrentSession();
		return (Long)generator.generate((SessionImplementor)session, null);
	}