Cookie的简单实例；

@WebServlet("/CookieTestServlet")
public class CookieTestServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置响应的消息体的数据格式以及编码
        response.setContentType("text/html;charset=UTF-8");
        //1.获取所有的Cookie
        Cookie[] cookies = request.getCookies();
        //有没有cookies为lastTime
        boolean flag = false;
        //2.遍历Cookie数组
        if (cookies != null && cookies.length > 0){
            for (Cookie cookie : cookies) {
                //获取Cookie的名称
                String name = cookie.getName();
                //判断名称是否是Lasttime
                if("lastTime".equals(name)){
                    //找到lastTime
                    //有Cookie，不是第一次访问
                    flag = true;
                    //设置Cookie的value
                    //获取当期时间的字符串，重新设置Cookie的值，重新发送cookie
                    Date date = new Date();
                    SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
                    String formatDate = sdf.format(date);
                    System.out.println("编码前:"+formatDate);
                    //url编码
                    String encode = URLEncoder.encode(formatDate, "utf-8");
                    System.out.println("编码后:"+encode);
                    cookie.setValue(encode);
                    //设置Cookie的存活时间
                    cookie.setMaxAge(60*60*24*30);  //一个月
                    response.addCookie(cookie);
                    //响应数据
                    //获取Cookie的value，时间
                    String value = cookie.getValue();
                    //URL解码
                    String decode = URLDecoder.decode(value, "utf-8");
                    response.getWriter().write("<h1>欢迎回来，您上次访问的时间为："+decode+"</h1>");
                    break;
                }
            }
        }
        if (cookies == null ||cookies.length<0||flag==false){
            //设置Cookie的value
            //获取当期时间的字符串，重新设置Cookie的值，重新发送cookie
            Date date = new Date();
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
            String formatDate = sdf.format(date);
            //url编码
            String encode = URLEncoder.encode(formatDate, "UTF-8");
            Cookie cookie = new Cookie("lastTime",encode);
            //设置Cookie的存活时间
            cookie.setMaxAge(60*60*24*30);  //一个月
            response.addCookie(cookie);
            response.getWriter().write("<h1>欢迎回来，您首次访问</h1>");
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}