Cookie如何在servlet 中使用

package com.learn;import javax.servlet.ServletException;import javax.servlet.http.Cookie;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.IOException;import java.io.PrintWriter;public class CookieServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {  //cookie引用  Cookie cookie = null;  //设置返回类型为文本类型  resp.setContentType("text/plain");  //获取输出对象  PrintWriter out = resp.getWriter();  //从请求参数中获取cookies  Cookie[] cookies = req.getCookies();  if(cookies != null){   for (int i = 0; i < cookies.length ; i++) {    out.println("name:"+cookies[i].getName());    out.println("value:"+cookies[i].getValue());    //如果cookie值为user，则赋值给cookie    if(cookies[i].getName().equals("user")){     cookie = cookies[i];    }   }  } else {   out.print("no cookie");  }  if(cookie == null){   cookie = new Cookie("user","tom");   //设置cookie最大值为60分钟   cookie.setMaxAge(60*60);   resp.addCookie(cookie);  } else if(cookie.getValue().equals("tom")){   cookie.setValue("jack");   resp.addCookie(cookie);  } else if(cookie.getValue().equals("jack")){   cookie.setMaxAge(0);   resp.addCookie(cookie);  }  out.close(); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {  super.doPost(req, resp); }}