文章目录
Cookie和Session会话保存会话的两种技术Cookie实现显示上次访问时间SessionSession的使用session实现购物车功能Cookie和Session
会话
会话:用户打开一个浏览器,点击了很多超链接,访问多个web资源,关闭浏览器,这个过程可以称之为会话;
有状态会话:一个同学来过教室,下次再来教室,我们会知道这个同学,曾经来过,称之为有状态会话;
一个网站,怎么证明你来过?
客户端 服务端
服务端给客户端一个 信件,客户端下次访问服务端带上信件就可以了; cookie服务器登记你来过了,下次你来的时候我来匹配你; seesion
保存会话的两种技术
cookie
客户端技术 (响应,请求)
session
服务器技术,利用这个技术,可以保存用户的会话信息? 我们可以把信息或者数据放在Session中!
常见场景:网站登录之后,你下次不用再登录了,第二次访问直接就上去了!
Cookie
从请求中拿到cookie信息服务器响应给客户端cookie实现显示上次访问时间
public class CookieServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//解决中文乱码问题resp.setContentType("text/html");req.setCharacterEncoding("utf-8");resp.setCharacterEncoding("utf-8");//获取cookieCookie[] cookies = req.getCookies();PrintWriter out = resp.getWriter();if (cookies!=null){out.print("你上一次访问的时间是:");for (int i = 0; i <cookies.length ; i++) {Cookie cookie = cookies[i];//获取cookie的键if (cookie.getName().equals("timing")){//获取cookie的值long lasteLoginTime = Long.parseLong(cookie.getValue());Date date = new Date(lasteLoginTime);out.print(date.toLocaleString());}}}else {out.print("这是你第一次访问");}//创建一个cookie存放上次访问的时间Cookie cookie = new Cookie("timing",System.currentTimeMillis()+"");//设置cookie存活时间为1天cookie.setMaxAge(24*60*60);//添加cookieresp.addCookie(cookie);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}}
第一次访问
第二次访问
有的浏览器第一次就会有一些cookie,这里用的是Microsoft edge。
Session
什么是Session:
服务器会给每一个用户(浏览器)创建一个Seesion对象;一个Seesion独占一个浏览器,只要浏览器没有关闭,这个Session就存在;用户登录之后,整个网站它都可以访问!
Session和cookie的区别:
Cookie是把用户的数据写给用户的浏览器,浏览器保存 (可以保存多个)Session把用户的数据写到用户独占Session中,服务器端保存 (保存重要的信息,减少服务器资源的浪费)Session对象由服务创建;
使用场景:
保存一个登录用户的信息;购物车信息;在整个网站中经常会使用的数据,我们将它保存在Session中;
Session的使用
得到session并向其中存放person对象,输出sessionID信息
public class SessionDemo01 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//解决中文乱码问题resp.setCharacterEncoding("utf-8");resp.setContentType("text/html;charset=utf-8");req.setCharacterEncoding("utf-8");//得到SessionHttpSession session = req.getSession();//向session中存东西session.setAttribute("person",new Person("伊泽瑞尔",18));//存放session idString id = session.getId();if (session!=null){resp.getWriter().write("session创建成功,id为:"+id);}else {resp.getWriter().write("session已经存在,id为:"+id);}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}}
后台输出session对象信息
public class SessionDemo02 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//解决中文乱码问题resp.setCharacterEncoding("utf-8");resp.setContentType("text/html;charset=utf-8");req.setCharacterEncoding("utf-8");//得到SessionHttpSession session = req.getSession();Person person = (Person) session.getAttribute("person");System.out.println(person.toString());}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}}
手动注销session
public class SessionDemo03 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//解决中文乱码问题resp.setCharacterEncoding("utf-8");resp.setContentType("text/html;charset=utf-8");req.setCharacterEncoding("utf-8");//得到SessionHttpSession session = req.getSession();session.removeAttribute("person");//手动注销sessionsession.invalidate();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}}
设置session失效时间
<session-config><!--设置session失效时间为1分钟--><session-timeout>1</session-timeout></session-config>
第一次访问页面创建了一个sessionID
访问SessionDemo02后台输出session保存的person对象信息
访问SessionDemo03注销session
再次访问SessionDemo01又新创建了一个session,id和第一次访问的不同。
session实现购物车功能
jsp页面
<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head><title>Title</title></head><body><h1>请选择你要购买的书籍</h1><form action="${pageContext.request.contextPath}/ShoppingCarDemo01" method="get"><input type="checkbox" name="book" value="JavaSE"/>JavaSE <br/><input type="checkbox" name="book" value="JavaWeb"/>JavaWeb <br/><input type="checkbox" name="book" value="JavaEE"/>JavaEE <br/><input type="submit" value="提交"></form></body></html>
处理书籍信息的servlet
public class ShoppingCarDemo01 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//解决中文乱码问题resp.setCharacterEncoding("utf-8");resp.setContentType("text/html;charset=utf-8");req.setCharacterEncoding("utf-8");//获取session对象HttpSession session = req.getSession();Map<String,Integer> car = (Map<String, Integer>) session.getAttribute("shoppingCar");if(car==null){car = new HashMap<>();}//获取客户端数据String[] books = req.getParameterValues("book");if (books!=null && books.length>0){for (String book : books) {if (car.get(book)!=null){int num = car.get(book);car.put(book,num+1);}else {car.put(book,1);}}}session.setAttribute("shoppingCar",car);//重定向到购物车页面resp.sendRedirect("/demo02_war/ShoppingCarDemo02");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}}
显示购物车信息的servlet
public class ShoppingCarDemo02 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//解决中文乱码问题resp.setCharacterEncoding("utf-8");resp.setContentType("text/html;charset=utf-8");req.setCharacterEncoding("utf-8");PrintWriter out = resp.getWriter();//获取session对象HttpSession session = req.getSession();Map<String,Integer> car = (Map<String, Integer>) session.getAttribute("shoppingCar");if (car != null &&car.size()>0){out.print("您购买的书籍有");for (String bookName : car.keySet()) {out.print("<p>"+bookName+":"+car.get(bookName)+"本<p>");}}else {out.print("您还未购买任何书籍");}out.print("<p><a href='bookChoose.jsp'>继续购买</a></p>");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}}
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