protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {		// TODO Auto-generated method stub		super.doGet(req, resp);				String signature=req.getParameter("signature");		String timestamp=req.getParameter("timestamp");		String nonce=req.getParameter("nonce");		String echostr=req.getParameter("echostr");						PrintWriter out=resp.getWriter();		if(CheckUtil.checkSignature(signature, timestamp, nonce)) {			out.println(echostr);		}	}