package  net.fpestde.test.tree;

 import  ...;

 public   class  ProductTreeFactory  extends  AbstractTreeFactory {
   public   static   final  String TREE_NAME = "sptree";

  // получение списка групп у которых парентом является parentGroup
   protected  List getGroups(ProductGroup parentGroup)  throws  SQLException {
    String qry = "select * from your_groups where parentId ";

    String orderClause = "order by name";

    qry += (parentGroup ==  null ) ?
            "is null " + orderClause :
            "= ? " + orderClause;
    
    Connection con = ...;

    List list =  new  ArrayList();

     try  {
      PreparedStatement st = con.prepareStatement(qry);
       if  (parentGroup !=  null )
        st.setLong( 1 , parentGroup.getId());

      ResultSet rs = st.executeQuery();
       while  (rs.next()) {
        String name = rs.getString("name");
         int  id = rs.getInt("id");
         int  parentId = rs.getInt("parentId");
        ProductGroup group =  new  ProductGroup(id, name, parentId);
        list.add(group);
      }
      rs.close();
    }  finally  {
      con.close();
    }
     return  list;
  }

   protected  String getHref() {
     return  "some.servlet.which.show.products.in.group.do";
  }
}

 package  net.fpestde.test.tree;

 import  net.sf.jsptree. ...;
 import  ...;

 public   abstract   class  AbstractTreeFactory  implements  TreeFactory {
   protected  Tree buildedTree;
   protected   boolean  openTree;

   public  Tree getTree(String name) {
    // возвращаем дерево в любом случае :)
     if  (buildedTree ==  null ) {
      buildedTree = buildTree();
    }
     return  buildedTree;
  }

   protected   abstract  List getGroups(ProductGroup parentGroup)  throws  SQLException;

   protected   abstract  String getHref();

   protected  Tree buildTree() {
    JSPTreeNodeImpl node =  new  JSPTreeNodeImpl();
    node.setContextRelative(false);
    node.setId("");
    node.setLabel("");
    
    TreeModel model =  new  TreeModel();
    model.setRoot(node);

     try  {
      List list = getGroups( null );
       for  ( int  i =  0 ; i < list.size(); i++) {
        ProductGroup group = (ProductGroup) list.get(i);
        fillGroup(model, node, group);
      }

    }  catch  (Exception e) {
      // :)
    }

     return  a_model;
  }

   protected   void  fillGroup(TreeModel model, JSPTreeNode parent, ProductGroup group)  throws  Exception {
    JSPTreeNodeImpl node =  new  JSPTreeNodeImpl(String.valueOf(group.getId()), group.getName());

    node.setHref(getHref() + "?gid=" + group.getId());
    node.setContextRelative(false);

    model.addChildToParent(parent, node);

     if  (isOpenTree())
      model.openNode(node);

    List list = getGroups(group);
     for  ( int  i =  0 ; list !=  null  && i < list.size(); i++) {
      ProductGroup g = (ProductGroup) list.get(i);
      fillGroup(model, node, g);
    }
  }

   public  Tree reloadTree() {
     synchronized  ( this ) {
      TreeModel model = (TreeModel) buildTree();
      TreeNode root = model.getRootNode();
       if  (buildedTree !=  null ) {
        List children = root.getChildNodes();
         for  ( int  i =  0 ; i < children.size(); i++) {
          TreeNode node = (TreeNode) children.get(i);
          checkOpened(model, node);
        }
      }

      buildedTree = model;
    }
     return  buildedTree;
  }

   private   void  checkOpened(TreeModel tree, TreeNode node) {
     if  (buildedTree.isNodeOpened(node.getData()))
      tree.openNode(node.getData());

    List children = node.getChildNodes();
     for  ( int  i =  0 ; i < children.size(); i++) {
      TreeNode treeNode = (TreeNode) children.get(i);
      checkOpened(tree, treeNode);
    }
  }

   public   boolean  isOpenTree() {
     return  openTree;
  }

   public   void  setOpenTree( boolean  openTree) {
     this .openTree = openTree;
  }
}

...
<%
  ProductTreeFactory treeFactory = (ProductTreeFactory) session.getAttribute("myfactory");
  if (treeFactory == null) {
    treeFactory = new ProductTreeFactory();
    session.setAttribute("myfactory", treeFactory);
  }
%>
<jtree:JSPTree name="<%=ProductTreeFactory.TREE_NAME%>"
                     treeFactory="<%=treeFactory%>"
                     startAtDepth="1"
                     imagesPath="images/tree/folder/orange/"
                     templatePath="template/folder/"
                     stateManagerAction="some.servlet.action.do"
                     nodeComparator="net.fpestde.test.tree.GroupComparator"
                     skin="net.fpestde.test.tree.GroupTreeSkin"/>

...

 package  net.fpestde.test.tree;

 import  net.sf.jsptree. ...;

 import  java.util.Comparator;

 public   class  GroupComparator  implements  Comparator{
   public   int  compare(Object o1, Object o2) {
     if  (!(o1  instanceof  TreeNode && o2  instanceof  TreeNode))
       return   0 ;

    TreeNode node1 = (TreeNode) o1;
    TreeNode node2 = (TreeNode) o2;

    JSPTreeNode jsp_node1 = (JSPTreeNode) node1.getData();
    JSPTreeNode jsp_node2 = (JSPTreeNode) node2.getData();

     return  jsp_node1.getLabel().compareTo(jsp_node2.getLabel());
  }  
}

 package  net.fpestde.test.tree;

 import  net.sf.jsptree. ...;

 import  ...;

 public   class  GroupTreeSkin  extends  FolderTemplateSkin {
  // пример реализации этого класса можно посмотреть в примерах пакета
  // net.sf.jsptree
  // 
  // у меня время свободное кончилось :)) будут проблемы - пиши
}