Jagat Pandya:
HttpServletRequest httpRequest = (HttpServletRequest) (FacesContext
.getCurrentInstance().getExternalContext().getRequestMap()
.get("com.liferay.portal.kernel.servlet.PortletServletRequest"));
Wrong wrong wrong.
First, the OP's code fails because:
1FacesContext fc = FacesContext.getCurrentInstance();
2HttpServletRequest request = (HttpServletRequest) fc.getExternalContext().getRequest();
The request instance is a PortletRequest, not an HttpServletRequest. Cast it to a PortletRequest and you're fine.
Second, if you need the original HttpServletRequest (which I highly doubt because no one in the portlet world typically needs this request), you use the com.liferay.portal.util.PortalUtil.getHttpServletRequest(PortletRequest) to access it.
Do not attempt Jagat's 'back door' access because it may break in the future, where the API will be maintained.