JAVA EE-SESSION&COOKIE

应该相信，自己是生活的战胜者。 —— 雨果

什么是会话技术？

• 会话的概念:
  日常生活来讲.会话就是两个人聊天. 聊天的前提,聊天双方需要有记忆力. 在聊的过程中,都是基于之前聊的状态,继续往下聊.
  我们javaweb中,浏览器和服务器也可以看作是双方在聊天(请求,响应). 浏览器服务器双方也需要有”记忆力”,保存之前的聊天状态.服务器和浏览器才可以完成会话.
• 会话的范围:
  两个从打招呼到两人互相道别.是一次会话.
  打开网站,完成我们想做的需求,到关闭浏览器.是一次会话.
  Cookie: 让浏览器能够记录信息.
  Session:让服务器端能够记录信息.

Cookie与Session的图解

详解Cookie技术

演示向浏览器发送cookie头

//演示发送cookie(头)到浏览器public class AServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        //明白原理的写法:        //response.setHeader("set-Cookie", "name=tom");        //使用封装好的代码        //创建cookie对象 => 封装键值对        Cookie cookie = new Cookie("name",URLEncoder.encode("汤姆","UTF-8"));        //将cookie添加到response中 => 添加响应头        response.addCookie(cookie);    }}

演示如何取出浏览器发出来的cookie

//演示取出浏览器发送过来的cookiepublic class BServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        // 获得浏览器发送的所有cookie        Cookie[] cookies = request.getCookies();            Cookie nameCookie = null;        //遍历,找到我们要找的cookie        if(cookies!=null){            for(Cookie c : cookies){                if("name".equals(c.getName())){                    //找到了                    nameCookie = c;                 }            }        }        if(nameCookie!=null){            System.out.println("浏览器发送的cookie==>" + nameCookie.getName()+":"+nameCookie.getValue());            System.out.println("浏览器发送的cookie==>" + nameCookie.getName()+":"+URLDecoder.decode(nameCookie.getValue(), "UTF-8"));        }else{            System.out.println("没有找到namecookie");        }    }}

令人十分不解的是，SUN公司还没有对取出cookies进行优化，如果想取出特定键，必须遍历后判断。
但是我们可以通过自己封装一个工具类来实现取出特定Cookie的目的。

public class CookieUtils {    public static Cookie getCookieByName(HttpServletRequest request,String name){        Cookie cookie  = null;        Cookie[] cookies = request.getCookies();        if(cookies!=null){            for(Cookie c: cookies){                if(name.equals(c.getName())){                    cookie = c;                }            }        }        return cookie;    } }

设置cookie在何时后过期

public class CServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        Cookie c = new Cookie("name","jerry");        //设置cookie的有效时间            c.setMaxAge(60*60*24*7*2);//告诉浏览器保存2周            //c.setMaxAge(-1);// -1代表 在会话结束时删除cookie(默认情况)            //c.setMaxAge(0);// 通常用于删除已经存在的cookie.使用一个寿命为0的cookie,覆盖要删除的cookie        response.addCookie(c);    }}

设置Cookie的路径

public class DServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {            Cookie c  = new Cookie("name","jack");            //设置Cookie的路径            c.setPath("/day09-cookie/ABC");            response.addCookie(c);    }}

保存访问的历史纪录

public class EServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {//      1.获得参数            String name  = request.getParameter("name");//      2.获得Cookie            Cookie history = CookieUtils.getCookieByName(request, "history");            if(history!=null){//          //存在 => 修改cookie加上现在浏览器的品牌 => dell,hp,lenvo                if(!history.getValue().contains(name)){                history = new Cookie("history",history.getValue()+","+name);                }            }else{//          //不存在 => 创建cookie                history = new Cookie("history",name);            }//      3.将cookie发送会浏览器            response.addCookie(history);//      4.重定向到列表页面            response.sendRedirect("/day09-cookie/history/list.jsp");    }}

记住用户名与密码

public class FServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {//      1.获得用户名密码        String  name  = request.getParameter("name");//      2.校验用户名密码        if(name==null || "".equals(name.trim())){//          //失败=> 转发到表单页面,并提示错误            request.setAttribute("error", "请输入用户名!");            request.getRequestDispatcher("/remember/login.jsp").forward(request, response);            return;        }//      3.创建cookie 添加要保存的用户名,        Cookie c = new Cookie("remember", name);//      4.查看记住用户名是否被选中        String remember = request.getParameter("remember");        if("yes".equals(remember)){//          选中 => 设置保存时间为2周            c.setMaxAge(60*60*24*7*2);        }else{//          //没选中=>设置保存事件为0            c.setMaxAge(0);        }//      5.添加到响应中        response.addCookie(c);//      6.重定向到成功页面        response.sendRedirect("/day09-cookie/index.jsp");    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}

Session技术详解

如何获取Session对象

public class AServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {            //参数类型是boolean型            //true=> 无论如何都要获得session            //false => 如果没有sessionID ,不会获得session            //request.getSession(true);        HttpSession session =  request.getSession();//相当于上面的方法 填写true            //session 的操作//      session.setAttribute(arg0, arg1)//      session.getAttribute(arg0)//      session.getAttributeNames()//      session.removeAttribute(arg0)            //session中可以存放登录状态    }}

关于session对象的一些操作

public class BServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        HttpSession session = request.getSession();        System.out.println("session.isNew()"+session.isNew());// 判断session是否 是新的.        System.out.println("session.getCreationTime()"+new Date(session.getCreationTime()));//获得session的创建时间        System.out.println("session.getId()"+session.getId());//获得session的id        System.out.println("session.getLastAccessedTime()"+new Date(session.getLastAccessedTime()));//获得最后一次的访问时间        System.out.println("session.getMaxInactiveInterval()"+session.getMaxInactiveInterval());// 获得session的最大有效时间        //session.setMaxInactiveInterval(60);//设置session的最大有效时间为60秒        session.invalidate();//*** 立即让session销毁.    }}

Session的一些细节问题

Session的细节

    1.Session的有效时间        默认:            30分钟        手动指定:            * tomcat/conf/web.xml => <Session-timeout>            * 项目/WEB-INF/web.xml => <Session-timeout>            * 代码: session.setMaxInactiveInterval(); 每次调用只影响被调用的session对象    2.Session的作用范围        一个会话期间        会话结束:            1.浏览器关闭            2.Session的过期            3.手动调用销毁Session的方法    3.Session中的其他API        Session.invalidate() => 立即销毁Session对象 

利用Session与Cookie技术完成两个实例的制作

购物车

先构建左侧的购物车区域

  </head>  <body>    <h1>商品列表</h1>    <table border="1" >        <tr>            <td>                <img src="/day09-cart/img/pic (1).jpg" width="300" height="200" /><br>                肥皂<br>                <a href="/day09-cart/AServlet?name=0"  >点击加入购物车</a>            </td>            <td>                <img src="/day09-cart/img/pic (2).jpg" width="300" height="200" /><br>                蜡烛<br>                <a href="/day09-cart/AServlet?name=1" >点击加入购物车</a>            </td>        </tr>        <tr>            <td>                <img src="/day09-cart/img/pic (3).jpg" width="300" height="200" /><br>                被罩<br>                <a href="/day09-cart/AServlet?name=2" >点击加入购物车</a>            </td>            <td>                <img src="/day09-cart/img/pic (4).jpg"  width="300" height="200" /><br>                枕头<br>                <a href="/day09-cart/AServlet?name=3" >点击加入购物车</a>            </td>        </tr>    </table>        <a href="/day09-cart/cart.jsp" >查看购物车</a>  </body></html>

Servlet的业务逻辑代码

public class AServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        //0 准备数组,与页面商品对应        String[] products = {"肥皂","蜡烛","被罩","枕头"};//      1. 获得当前请求要添加的商品        String indexStr = request.getParameter("name");// 0 ~ 3         String productName = products[Integer.parseInt(indexStr)];//      2.从Session中取出存放购物车的map        Map<String,Integer> cart = (Map<String, Integer>) request.getSession().getAttribute("cart");        if(cart==null){//          //取不到=>初始化map,            cart = new LinkedHashMap<String, Integer>();            //并放入session            request.getSession().setAttribute("cart", cart);        }//      3.使用当前要添加的商品从map中取值            Integer count = cart.put(productName, 1);            if(count!=null){                cart.put(productName, count+1);            }//          //取不到=> 放入map,设置数量为1//          //取得到=> 将数量+1放回去//      4.重定向回商品列表页面            response.sendRedirect("/day09-cart/list.jsp");    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}

用于显示输出的JSP

**  </head>  <body>    <h1>购物车</h1>    <table border="1">        <tr>            <th>商品名称</th>            <th>商品数量</th>        </tr>        <%            Map<String,Integer> cart = (Map<String,Integer>)session.getAttribute("cart");            if(cart!=null && cart.size()>0){                for(Entry<String,Integer> en : cart.entrySet()){                %>                <tr>                    <td><%=en.getKey() %></td>                    <td><%=en.getValue() %></td>                </tr>                <% }            }         %>    </table>  </body></html>**

验证码

生成验证码并且发送给浏览器的代码逻辑

public class AServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {            //0设置正文类型        response.setContentType("image/jpeg");            //1 生成验证码        ValidateCode code = new ValidateCode(150, 70, 4, 2);            //2 将正确答案放入Session        String str =  code.getCode();        request.getSession().setAttribute("code", str);        System.out.println(str);            //3 将图片流发送给浏览器        code.write(response.getOutputStream());    }}

获取并且判断

public class BServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        //1 获得用户填写的验证码            String code1 = request.getParameter("code");        //2 获得Session中正确的            String code2 = (String) request.getSession().getAttribute("code");        //3 比对            if(code1!=null && code1.equalsIgnoreCase(code2)){                //成功=> 登录成功 => 重定向到登录页面                response.sendRedirect("/day09-checkcode/index.jsp");            }else{                //失败=> 转发到登录页面并提示                request.setAttribute("error", "请输入正确的验证码");                request.getRequestDispatcher("/login.jsp").forward(request, response);            }    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}

最终显示的JSP代码

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <base href="<%=basePath%>">    <title>My JSP 'login.jsp' starting page</title>    <meta http-equiv="pragma" content="no-cache">    <meta http-equiv="cache-control" content="no-cache">    <meta http-equiv="expires" content="0">        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">    <meta http-equiv="description" content="This is my page">    <!--    <link rel="stylesheet" type="text/css" href="styles.css">    -->    <script type="text/javascript">    function fun1(){ // 改变img标签的src属性值        //1 获得img标签对象        var img = document.getElementById("one");        //2 改变src属性        img.src = "/day09-checkcode/AServlet?date="+new Date();    }    </script>  </head>  <body>  <form action="/day09-checkcode/BServlet"  >        用户名:<input type="text" name="name" /> <br>        密码:<input type="text" name="password" /><br>        验证码:<input type="text" name="code" size="4" /><img id="one" src="/day09-checkcode/AServlet" >         <a href="javaScript:void(0)" onclick="fun1();" >看不清,换一张</a>        <font color="red" >${requestScope.error}</font>        <br>        <input type="submit" value="登录" />    </form>  </body></html>