cookie小试刀—编写servlet利用Cookie保存上次访问该servlet的时间

来源：互联网发布：linux 查看系统信息编辑：程序博客网时间：2024/06/06 01:36

简单分析，由于http协议的无状态性不能保存数据，我们利用cookie保存用户上次登陆该servlet的时间，第一次登陆告诉是第一次登陆还没记录，（servlet中获取到的cookie值为空说明是第一次登陆这时设置上cookie的值保存这次登陆的时间）第二次及以后则显示上次的登陆时间（servlet中获取到的cookie值不为空，将cookie中的值显示即上次登录的时间）。

代码：

package com.zc.servlet;import java.io.IOException;import java.io.PrintWriter;import java.util.Calendar;import java.util.GregorianCalendar;import javax.servlet.ServletException;import javax.servlet.http.Cookie;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class TestCookie2 extends HttpServlet {/** *  */private static final long serialVersionUID = 1L;/** * Constructor of the object. */public TestCookie2() {super();}/** * Destruction of the servlet. <br> */public void destroy() {super.destroy(); // Just puts "destroy" string in log// Put your code here}/** * The doGet method of the servlet. <br> *  * This method is called when a form has its tag value method equals to get. *  * @param request *            the request send by the client to the server * @param response *            the response send by the server to the client * @throws ServletException *             if an error occurred * @throws IOException *             if an error occurred */public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doPost(request,response);}/** * The doPost method of the servlet. <br> *  * This method is called when a form has its tag value method equals to * post. *  * @param request *            the request send by the client to the server * @param response *            the response send by the server to the client * @throws ServletException *             if an error occurred * @throws IOException *             if an error occurred */public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("text/html;charset=utf-8");PrintWriter out = response.getWriter();/*获取上册登陆的时间*/GregorianCalendar gc=new GregorianCalendar();String time=gc.get(Calendar.YEAR)+"-"+gc.get(Calendar.MONTH)+"-"+gc.get(Calendar.DATE)+"-"+gc.get(Calendar.HOUR)+":"+gc.get(Calendar.MINUTE)+":"+gc.get(Calendar.SECOND);//存放系统获取的时间if(gc.get(Calendar.AM_PM)==1){//判断上次登陆是上午还是下午time+="  PM";}else{time+="  AM";}Cookie timeCookie = new Cookie("lastTime",time);//存放上次登录时间的cookietimeCookie.setMaxAge(3600*24*365);//设置cookie的有效时间是一年response.addCookie(timeCookie);//添加时间cookieCookie[] Cookies = request.getCookies();//获取所有cookieString lastTime=null;//存放上次登陆的时间for(int i=0;Cookies!=null&&i<Cookies.length;i++){if("lastTime".equals(Cookies[i].getName())){lastTime=Cookies[i].getValue();break;}}out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");out.println("<HTML>");out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");out.println("  <BODY>");if(lastTime==null){out.println("您是第一次登陆");}else{out.println("上次登陆的时间是："+lastTime);}out.println("  </BODY>");out.println("</HTML>");out.flush();out.close();}/** * Initialization of the servlet. <br> *  * @throws ServletException *             if an error occurs */public void init() throws ServletException {// Put your code here}}

从上面的试验中可以看出cookie保存的总是上一次访问该网站时的信息。