res.setContentType("text/html");
PrintWriter out = res.getWriter();
String code = null, message = null, type = null;
Object codeObj, messageObj, typeObj;
// Retrieve the three possible error attributes, some may be null
codeObj = req.getAttribute("javax.servlet.error.status_code");
messageObj = req.getAttribute("javax.servlet.error.message");
typeObj = req.getAttribute("javax.servlet.error.exception_type");
// Convert the attributes to string values
if (codeObj != null) code = codeObj.toString();
if (messageObj != null) message = messageObj.toString();
if (typeObj != null) type = typeObj.toString();
// The error reason is either the status code or exception type
String reason = (code != null ? code : type);
out.println("<HTML>");
out.println("<HEAD><TITLE>" + reason + ": " + message + "</TITLE></HEAD>");
out.println("<BODY>");
out.println("<H1>" + reason + "</H1>");
out.println("<H2>" + message + "</H2>");
out.println("<HR>");
out.println("<I>Error accessing " + req.getRequestURI() + "</I>");
out.println("</BODY></HTML>");
