JXTreeTable selection by code

Question

I need to ask for a little hint about node selection in my JXTreeTable.

I added some nodes to it and want to select one node as Default by program. My test function for selecting a node looks like this:

public void setSelectionTest()
{        
    Object                      dfltObj;
    TreeSelectionModel          tsm             =   jttRulesSet.getTreeSelectionModel();
    TreeTableModelRules         ttm             =   (TreeTableModelRules)jttRulesSet.getTreeTableModel();
    TreePath                    tp;

    dfltObj                                     =   ttm.getChild(ttm.getRoot(), 0);
    if( (dfltObj != null) )
    {
        System.out.println("Node to select: " + dfltObj.getClass());
        tp                                      =   new TreePath(dfltObj);
        tsm.setSelectionPath(tp);
        jttRulesSet.scrollPathToVisible(tp);
    }

My test function for verifiing the effect:

public void getSelectionTest()
{
     TreeSelectionModel             tsm;
     TreePath                       treeSelPath;

     Object                         dfltNode;

     tsm                                        =   jttRulesSet.getTreeSelectionModel();            // get treeselectionmodel
     treeSelPath                                =   tsm.getSelectionPath();                         // get selected path 
     if(treeSelPath != null)
     {
         dfltNode                               =   treeSelPath.getLastPathComponent();
         System.out.println("Selected node: " + ((RulesSet) dfltNode).getName());                   // info bout the selected path
         System.out.println("Selected node: " + tsm.getSelectionCount());
     }
}   

I get Name and number of selected row. So far OK. But the JXTreeTable shows no selection. The jttRulesSet.expandPath(tp) line has no effect as well. There must be an undiscovered fact behind...

Can somebody give me any tip to solve this problem?