out.println("<h2>Show subparts of a part : <a href=\"C:/Documents and Settings/DbWeb/src/java/Servlets/ClientService.java?action=loadPartInfo&Part="+childPart+"\">"+childPart.getObject_Id()+"</a></h2>");                

...
 protected   void  processRequest(HttpServletRequest request, HttpServletResponse response)
     throws  ServletException, IOException 
    {
       response.setContentType("text/html;charset=UTF-8");
       String Action = request.getParameter("action");
       
         if  (Action== null )
        {
            // no action yet, show the welcome page
            RequestDispatcher disp = getServletContext().getRequestDispatcher("/defaultPage.jsp");
            disp.include(request, response); 
             return ;
        }
         if  (Action.equals("LoadPartInfo"))
        {
            String SearchedPart = request.getParameter("Part");

             if  ((SearchedPart!= null ) && (SearchedPart!="")) 
            {       
                        //to  look in DB for Subparts of SearchedPart
            }
        }
         else ...
}

<a href=\"C:/Documents and Settings/DbWeb/build/
web/WEB-INF/classes/Servlets/ClientService?
action=loadPartInfo&Part="+childPart+"\">"+childPart.getObject_Id()+"</a></h2>");