失眠网 > Severlet会话管理之Cookie使用

Severlet会话管理之Cookie使用

时间：2020-02-01 10:23:44

分为两个severlet程序，第一个用于判断cookie，和根据cookie的情况决定是否对表单进行填充，打印form表单在界面上；第二个用于响应表单的请求，如果有“记住密码”，“xx天内免登录”等信息，则创建cookie。

第一个程序如下：

public void Service(HttpServletRequest request,HttpServletResponse response)throws ServletException, IOException{// 设置响应内容类型response.setContentType("text/html;charset=gb2312");request.setCharacterEncoding("gb2312");//在打印表单前，事先尝试获取CookieCookie cookie_number = null;Cookie cookie_password = null;String number = "";String password = "";Cookie []cookies = request.getCookies();if(cookies != null) {//System.out.println("cookies[]不为空");for(int i = 0; i<cookies.length; i++) {System.out.println(cookies[i].getName());if(cookies[i].getName().equals("number")) {cookie_number = cookies[i];number = cookie_number.getValue();}if(cookies[i].getName().equals("password")) {cookie_password = cookies[i];password = cookie_password.getValue();}}}// 实际逻辑PrintWriter out = response.getWriter();if(number.isEmpty() || password.isEmpty()) {//没有获取到cookie信息，仅仅正常打印表单System.out.println("未自动填写登录信息");try {out.println("<h1>Login</h1>");out.println("<form name=\"form\" method=\"post\" action=\"GetPostData\">");out.println("<input name=\"number\" type=\"text\" placeholder=\"请输入学号/工号\"/>");out.println("<br>");out.println("<input name=\"password\" type=\"password\" placeholder=\"请输入密码\"/>");out.println("<br>");out.println("<input name=\"CheckboxRememberPwd\" type=\"checkbox\">记住密码");out.println("<br>");out.println("<input name=\"submit_login\" type=\"submit\" value=\"登录\" style=\"color: white; font-family: bold; background: forestgreen; margin-top: 20px; margin-right: 20px\">");out.println("<input name=\"reset_input\" type=\"reset\" value=\"重置\" style=\"border: azure; background: aliceblue; color: gray\">");out.println("</form>");}finally {out.close();}}else {//获取到了完整的用户登录信息，自动填充表单System.out.println("已自动填写登录信息");System.out.println(number);number = URLDecoder.decode(number,"utf-8");System.out.println(number);try {out.println("<h1>Login</h1>");out.println("<form name=\"form\" method=\"post\" action=\"GetPostData\">");out.format("<input name=\"number\" type=\"text\" value=\"%s\"/>",number); //填充学号out.println("<br>");out.format("<input name=\"password\" type=\"password\" value=\"%s\"/>",password); //填充密码out.println("<br>");out.println("<input name=\"CheckboxRememberPwd\" type=\"checkbox\" checked>记住密码");out.println("<br>");out.println("<input name=\"submit_login\" type=\"submit\" value=\"登录\" style=\"color: white; font-family: bold; background: forestgreen; margin-top: 20px; margin-right: 20px\">");out.println("<input name=\"reset_input\" type=\"reset\" value=\"重置\" style=\"border: azure; background: aliceblue; color: gray\">");out.println("</form>");}finally {out.close();}}}

第二个程序：

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub//doGet(request, response);response.setContentType("text/html;charset=gb2312");request.setCharacterEncoding("gb2312");PrintWriter out = response.getWriter();if(request.getParameter("number").isEmpty() || request.getParameter("password").isEmpty()) {//判断学号，密码是否都不为空，为空则提示out.println("请完整输入学号密码");}else {try {out.println("<BODY>\n"+"<div align=center>"+"<h2>登录成功！</h2>\n"+"学号/工号："+request.getParameter("number")+"<br><br>"+"密码："+request.getParameter("password")+"<br><br>"+"记住密码状态："+request.getParameter("CheckboxRememberPwd")+"</div>"+"</BODY></HTML>");if(request.getParameter("CheckboxRememberPwd") == "null") {//用户没有选择“记住密码”System.out.println("用户没有选择“记住密码”");}else {//用户选择“记住密码”//Cookie操作Cookie []cookies = request.getCookies();Cookie cookie_number = null;Cookie cookie_password = null;boolean IsModify = false; //最新提交的表单与cookie存储是否不同if(cookies != null) {for(int i = 0; i<cookies.length; i++) {if(cookies[i].getName().equals("number")) {cookie_number = cookies[i];if(!cookies[i].getValue().equals(request.getParameter("number"))) {cookie_number.setValue(request.getParameter("number"));IsModify = true;}}if(cookies[i].getName().equals("password")) {cookie_password = cookies[i];if(!cookies[i].getValue().equals(request.getParameter("password"))) {cookie_number.setValue(request.getParameter("password"));IsModify = true;}}}}if(cookie_number==null || cookie_password==null || IsModify) {//首次登录或者客户端删除了cookie数据或者更新了新的学号密码//System.out.println("添加cookie到响应返回给客户端");String number = URLEncoder.encode(request.getParameter("number"),"utf-8"); //解决中文乱码cookie_number = new Cookie("number",number);cookie_password = new Cookie("password",request.getParameter("password"));cookie_number.setPath(request.getContextPath());cookie_password.setPath("/");cookie_number.setHttpOnly(true);cookie_password.setHttpOnly(true);cookie_number.setMaxAge(60*60*24*30); //设置为一个月cookie_password.setMaxAge(60*60*24*30);response.addCookie(cookie_number);response.addCookie(cookie_password);}}}finally {out.close();}}}

遇到问题：

cookie不生效，原因：response.addCookie(cookie);这一句一定要写在out.close();这一句话之前。console发出警告：

在路径为[/Severlet_First]的上下文中，servlet[GetPost]的Servlet.service()引发异常

我是因为测试中文乱码问题产生的警告，只需要利用number = URLDecoder.decode(number,"utf-8");从cookie中取出后解码成中文，String number = URLEncoder.encode(request.getParameter("number"),"utf-8");，在存入cookie之前编译成utf-8即可。