Like most portlet developments, there are some scenarios where you might need to retrieve HttpServletRequest and HttpServletResponse from Portlet Request (RenderRequest/RenderResponse/ActionRequest/ActionResponse etc).
In WebSphere Portal, there is a PortletUtils utility class that provides the method you need:
import com.ibm.ws.portletcontainer.portlet.PortletUtils; // call the respective methods to get HttpServletRequest/HttpServletResponse you need PortletUtils.getHttpServletRequest(request);
[10/9/2014]: As highlighted by Stefan Schmitt, the above mentioned method is not supported by IBM. We found out about this class when we de-compiled “Sitemap” portlet. There is 7 or more PortletUtils types if you viewed it from your RAD “Quick fix”, use it at your own discretion.