MockHttpServletResponse filterResponse = new MockHttpServletResponse();
ByteArrayOutputStream filterbaos = new ByteArrayOutputStream();
filterResponse.setOutputStream(filterbaos);
spEmpl.doFilter(filterRequest, filterResponse, new MockFilterChain());
String spResponse = new String(filterbaos.toByteArray());
Document spHTMLResponse = DocumentUtil.getDocument(spResponse);
NodeList nodes = spHTMLResponse.getElementsByTagName("INPUT");
Element inputElement = (Element) nodes.item(0);
String idpResponse = inputElement.getAttributeNode("VALUE").getValue();