jpql查询中的Category / Subcategory / SubSubcategory

Question

我必须使用JPQL显示我的jsf页面中每个类别的所有子类别。 我有一个Category（idCategory，name，idParent）表。我怎样才能管理jpql查询，以便向我展示所有类别的层次结构？

SQL查询就像下面这样：

select root.name  as root_name
 , down1.name as down1_name
 , down2.name as down2_name
 , down3.name as down3_name

   from  category as root
   left outer join category as down1
     on down1.parent = root.category_id
   left outer join category as down2
     on down2.parent = down1.category_id
   left outer join category as down3
     on down3.parent = down2.category_id
   where root.parent is null  

   order by 
      root_name 
    , down1_name 
    , down2_name 
    , down3_name
  ;

感谢。