<class
    name="domain.bo.Comment"
    table="guest_comment"
    dynamic-update="true"
    dynamic-insert="true"
>

    <id
        name="id"
        type="java.lang.Long"
        unsaved-value="null"
    >
        <column name="ID" sql-type="NUMBER" not-null="true"/>
        <generator class="sequence">
                <param name="sequence">guest_comment_id_seq</param>
        </generator>
    </id>

    <property
        name="parentId"
        type="java.lang.Long"
    >
        <column name="REF" sql-type="NUMBER" not-null="true"/>
    </property>

</class>



  <sql-query name="domain.bo.Comment.treeChildrenByRootId">
    <return alias="comment" class="domain.bo.Comment">
      <return-property name="id" column="id"/>
      <return-property name="parentId" column="parentId"/>
      <return-property name="hierarchicalLevel" column="hierarchicalLevel"/>
    </return>
select comment.ID AS id, comment.REF AS parentId, LEVEL AS hierarchicalLevel
from guest_comment comment
start with comment.ID= :rootId connect by comment.REF = prior comment.ID
  </sql-query>

  <sql-query name="domain.bo.Comment.treeChildrenByRootId">
    <return alias="comment" class="domain.bo.Comment">
      <return-property name="id" column="id"/>
      <return-property name="parentId" column="parentId"/>
      <return-property name="hierarchicalLevel" column="hierarchicalLevel"/>
    </return>
[b]    <return-scalar type="int" column="hierarchicalLevel"/>[/b]
select comment.ID AS id, comment.REF AS parentId, LEVEL AS hierarchicalLevel
from guest_comment comment
start with comment.ID= :rootId connect by comment.REF = prior comment.ID
  </sql-query>

        Object[] row = (Object[])i.next();
        Comment child = (Comment)row[1];
        child.setHierarchicalLevel(((Integer)row[0]).intValue());