To make configurable the class created by the PortletRequestHelperFactory, there should be a new config line in the displaytag.properties file with the complete name (package name + class name) of the class. Then, the PortletRequestHelperFactory's getRequestHelperInstance method should be changed to something similar to this:

        String className = //GET THE CLASSNAME FROM THE displaytag.properties
        if (className!=null && !"".equals(className)) {
         try {
         Class requestHelperClass = Class.forName(className);
         Constructor requestHelperConstructor = requestHelperClass.getConstructor(new Class[]{javax.servlet.jsp.PageContext.class});
         retorno = (RequestHelper)requestHelperConstructor.newInstance(new Object[]{pageContext});
         } catch (Exception e) {
         //do whatever is needed (by example, the exception should be logged)
         }
        } else {
        //do whatever is needed (by example, className not finded should be logged)
        }