Cookie和Session解决http的参数传递

Cookie

Cookie:小甜点 , 是客户端技术,将我们的共享数据保存到客户端(浏览器)    后面再请求的时候就会将共享数据发送到服务器.

此Cookie的作用就是 :我打个比方, 就是你去超市买东西,而你想要优惠的话就必须要办会员卡,而这会员卡就想Cookie,你下次再进来买东西就只要带会员卡就能证明你的身份了.

看了我上一张博客是有结构的,不懂结构的话可能会有点蒙:

@WebServlet("/cookie/login")public class LoginServlet extends HttpServlet{private static final long serialVersionUID = 1L;protected void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {//设置请求格式req.setCharacterEncoding("utf-8");//设置响应格式resp.setContentType("text/html;charset=utf-8");PrintWriter out = resp.getWriter();//获取请求时的用户名和密码String username = req.getParameter("username");String password = req.getParameter("password");//创建Cookie对象 这是重点Cookie c = new Cookie("username",username);resp.addCookie(c);//验证用户名和密码 在此我账号密码写死 if("admin".equals(username)&&"1234".equals(password)){//进入邮箱界面out.println("<h1>欢迎登录:"+username+"的邮箱</h1>");out.println("<a href='/dowork/cookie/list'>未读邮件</a>");}else{System.out.println("登录失败");}//关闭流out.close();}}

@WebServlet("/cookie/list")public class ListServlet extends HttpServlet{private static final long serialVersionUID = 1L;@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {//设置请求的格式req.setCharacterEncoding("utf-8");//设置响应格式resp.setContentType("text/html;charset=utf-8");//获取cookieCookie[] cookies = req.getCookies();String username = null;for (Cookie cookie : cookies) {if("username".equals(cookie.getName())){username = cookie.getValue();}}PrintWriter out = resp.getWriter();out.println("欢迎查看:"+username+"邮件");out.println("<a href = '/dowork/cookie/content'>邮件1</a>");out.println("<a href = '/dowork/cookie/content'>邮件2</a>");out.println("<a href = '/dowork/cookie/content'>邮件3</a>");out.close();}}

/** *  * @author AfricaYoung * @Date 2016-08-15 */@WebServlet("/cookie/content")public class ContentServlet extends HttpServlet{private static final long serialVersionUID = 1L;@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {req.setCharacterEncoding("utf-8");String username = null;Cookie[] cookies = req.getCookies();for (Cookie cookie : cookies) {if("username".equals(cookie.getName())){username = cookie.getValue();}}resp.setContentType("text/html;charset=utf-8");PrintWriter out = resp.getWriter();out.print("最后一页啦:"+username+"大大");out.print("<br/>宝宝炸了");out.close();}}

Cookie 的缺陷:
1.Cookie中的共享数据的类型只能是String类型,如果需要共享多个数据,就需要创建多个Cookie对象,很麻烦
2.Cookie不支持中文
3.Cookie是保存在浏览器中,不安全
4.Cookie有数据大小的限制,一个Cookie支持4kb  一个浏览器中只能保存300个Cookie信息  一个应用在一个浏览器中最多保存20个Cookie

Session

Session:会话,在浏览器打开的时候创建,浏览器关闭的时候销毁  是一个服务端的技术,将共享数据保存在服务器中 Session底层就是Cookie

/** *  * @author AfricaYoung * @Date 2016-08-15 */@WebServlet("/session/login")public class LoginServlet extends HttpServlet {private static final long serialVersionUID = 1L;@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {// 设置请求格式req.setCharacterEncoding("utf-8");// 设置响应格式resp.setContentType("text/html;charset=utf-8");PrintWriter out = resp.getWriter();// 获取请求时的用户名和密码String username = req.getParameter("username");String password = req.getParameter("password");// 获取sessionHttpSession session = req.getSession();session.setAttribute("USERNAME_IN_SESSION", username);// 修改共享数据// 验证用户名和密码if ("admin".equals(username) && "1234".equals(password)) {// 进入邮箱界面out.println("<h1>欢迎登录:" + username + "的邮箱</h1>");out.println("<a href='/dowork/session/list'>未读邮件</a>");// URL重写(浏览器可以禁用Cookie,这样我们的jsessionid就不能保存在浏览器中,那么服务器中的数据也就获取不到)// 方式:使用URL重写,自动的根据浏览器是否禁用Cookie来拼接jsessionidString url = resp.encodeURL("/dowork/session/list");out.print("<a href='" + url + "'>收件箱(4)</a><br/>");} else {System.out.println("登录失败");}out.close();}}

@WebServlet("/session/list")public class ListServlet extends HttpServlet{private static final long serialVersionUID = 1L;@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {//设置请求的格式req.setCharacterEncoding("utf-8");//设置响应格式resp.setContentType("text/html;charset=utf-8");String username = (String) req.getSession().getAttribute("USERNAME_IN_SESSION");PrintWriter out = resp.getWriter();out.println("欢迎查看:"+username+"邮件");out.println("<a href = '/dowork/session/content'>邮件1</a>");out.println("<a href = '/dowork/session/content'>邮件2</a>");out.println("<a href = '/dowork/session/content'>邮件3</a>");out.close();}}

@WebServlet("/session/content")public class ContentServlet extends HttpServlet{private static final long serialVersionUID = 1L;@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {req.setCharacterEncoding("utf-8");String username = (String) req.getSession().getAttribute("USERNAME_IN_SESSION");resp.setContentType("text/html;charset=utf-8");PrintWriter out = resp.getWriter();out.print("最后一页啦:"+username+"大大");out.print("<br/>宝宝炸了");out.close();}}