public static String buildNamespace(ActionMapper mapper,
    ValueStack stack,
    HttpServletRequest request) 
{
        ActionContext context = new ActionContext(stack.getContext());
        ActionInvocation invocation = context.getActionInvocation();
        if (invocation == null) {
            ActionMapping mapping = mapper.getMapping(request,
                    Dispatcher.getInstance().getConfigurationManager());
            if (mapping != null) {
                return mapping.getNamespace();
            } else {
                // well, if the ActionMapper can't tell us, and there is no existing action invocation,
                // let's just go with a default guess that the namespace is the last the path minus the
                // last part (/foo/bar/baz.xyz - > /foo/bar)
                String path = RequestUtils.getServletPath(request);
                return path.substring(0, path.lastIndexOf("/"));
            }
        } else {
            return invocation.getProxy().getNamespace();
        }
}

 public static ValueStack getStack(PageContext pageContext) 
{
        HttpServletRequest req = (HttpServletRequest) pageContext.getRequest();
        ValueStack stack = (ValueStack) req.getAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY);
        if (stack == null) {
            HttpServletResponse res = (HttpServletResponse) pageContext.getResponse();
            Dispatcher du = Dispatcher.getInstance();
            if (du == null) {
                throw new ConfigurationException("The Struts dispatcher cannot be found.  This is usually caused by "+
                        "using Struts tags without the associated filter. Struts tags are only usable when the request "+
                        "has passed through its servlet filter, which initializes the Struts dispatcher needed for this tag.");
            }
            stack = du.getContainer().getInstance(ValueStackFactory.class).createValueStack();
            Map< String, Object > extraContext = du.createContextMap(new RequestMap(req),
                    req.getParameterMap(),
                    new SessionMap(req),
                    new ApplicationMap(pageContext.getServletContext()),
                    req,
                    res,
                    pageContext.getServletContext());
            extraContext.put(ServletActionContext.PAGE_CONTEXT, pageContext);
            stack.getContext().putAll(extraContext);
            req.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, stack);
            // also tie this stack/context to the ThreadLocal
            ActionContext.setContext(new ActionContext(stack.getContext()));
        } else {
            // let's make sure that the current page context is in the action context
            Map< String, Object > context = stack.getContext();
            context.put(ServletActionContext.PAGE_CONTEXT, pageContext);
            AttributeMap attrMap = new AttributeMap(context);
            context.put("attr", attrMap);
        }
        return stack;
}