分析：
public class cookieServlet4 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");//设置消息体的数据格式以及编码
Cookie[] cs = request.getCookies();
if (cs!=null) {
int i =0;
for (Cookie c : cs) {
if((c.getName()).equals("lasttime"))
{
Date date = new Date();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
String str_date = sdf.format(date);
System.out.println("编码前"+str_date);
str_date = URLEncoder.encode(str_date,"utf-8");//URL编码
System.out.println("编码后"+str_date);
String value = c.getValue();
//URL解码
System.out.println("解码前："+value);
value = URLDecoder.decode(value,"utf-8");
response.getWriter().write("欢迎回来 你上次的访问时间是："+value);
c.setValue(str_date);
//设置存活时间
c.setMaxAge(60 * 60);
response.addCookie(c);
break;
}else if (cs.length==++i){//所有的cookie都不是last time 添加一个 name 为lasttime 的
Date date = new Date();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
String str_date = sdf.format(date);
str_date = URLEncoder.encode(str_date,"utf-8");
Cookie cookie = new Cookie("lasttime",str_date);
cookie.setMaxAge(60 * 60); //设置存活时间
response.addCookie(cookie);
response.getWriter().write("欢迎首次访问");
}
}
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}