Javaweb学习笔记day10---cookie_第1关:cookie 对象和常用 api 介绍-优快云博客

本文详细介绍了Web开发中的会话技术，包括Cookie和Session的概述、基本使用、执行流程、相关设置及销毁。讲解了Cookie的作用、属性、限制，以及创建、读取和销毁Cookie的方法。此外，还探讨了Session的工作原理，展示了如何在服务器端存储和共享数据，以及Session的配置和生命周期管理。

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会话技术介绍

为什么?
- ServletRequest域对象共享范围太小了，ServletContext域对象共享范围太大了。
概述
- 指的是web开发中的一次通话过程，当打开浏览器，访问网站地址后，会话开始，当关闭浏览器（或者到了过期时间），会话结束。
作用
- 存储数据并实现共享
分类
- Cookie : 浏览器端会话技术
- Session : 服务器端会话技术

cookie概述

概述
- 它是客户端浏览器的缓存文件，里面记录了客户浏览器访问网站的一些内容。同时，也是 HTTP协议请求头(Cookie)和响应头(Set-Cookie)的一部分
作用
- 它可以保存客户浏览器访问网站的相关内容（需要客户端不禁用Cookie）。从而在每次访问需要同一个内容时，先从本地缓存获取，使资源共享，提高效率。
常用属性
- name : cookie名称
- value : cookie值
- path : cookie访问路径
- maxAge : cookie存活时长

cookie的基本使用

需求
- ①创建Cookie对象
- ②将Cookie对象返回给浏览器并保存
- ③获取Cookie对象
代码实现

@WebServlet("/demo01")
public class Demo01Servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //①创建Cookie对象
        String msg = "hello";
        Cookie cookie = new Cookie("msg",msg);
        //②将Cookie对象返回给浏览器并保存
        response.addCookie(cookie);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

@WebServlet("/demo02")
public class Demo02Servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //③获取Cookie对象
        Cookie myCookie = null;//记录自己的Cookie对象
        Cookie[] cookies = request.getCookies();
        if (null != cookies && 0 != cookies.length) {
            for (Cookie cookie : cookies) {
                if ("msg".equals(cookie.getName())) {
                    myCookie = cookie;
                }
            }
        }
        if (null != myCookie) {
            System.out.println("name : " + myCookie.getName() + " , value : " + myCookie.getValue());
        } else {
            System.out.println("没有找到自己的cookie");
        }
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

cookie的执行流程

执行流程

①浏览器发起第一次请求Demo01Servlet(msg)
- 创建Cookie对象(name=msg,value=hello)
- 通过Set-Cookie响应头将Cookie对象携带回浏览器
②浏览器发起第二次请求Demo02Servlet(msg)
- 通过Cookie请求头将Cookie对象信息携带到服务器

cookie的相关设置

值限制
- Cookie 的值不能包含逗号、分号、空格，不能以$开头。
存活时长限制 : setMaxAge
- -1 : 默认值，浏览会话结束时
- 0 ：立即销毁
- 正数：设置cookie存活时长，以秒为单位
访问路径限制 : setPath
- 默认情况下，是"/项目访问路径"，访问项目下所有资源都会携带Cookie
- 完全匹配
  - 比如 : “/web15/xyz/index.html” , 只有"/web15/xyz/index.html"才会携带cookie
- 目录匹配
  - 比如："/web15/xyz"，"/web15/xyz/index.html"、"/web15/xyz/demo01.html"都会携带cookie

cookie的销毁

开发步骤
- ①创建Cookie对象
  - 设置相同的名称
- ②设置相同的访问路径
- ③设置maxAge=0
代码实现

@WebServlet("/demo06")
public class Demo06Servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie cookie = new Cookie("msg3", "hello3");
        cookie.setPath("/");
        response.addCookie(cookie);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

@WebServlet("/demo07")
public class Demo07Servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //①创建Cookie对象
        Cookie cookie = new Cookie("msg3", "helloworld");
        //②设置相同的访问路径
        cookie.setPath("/");
        //③设置maxAge=0
        cookie.setMaxAge(0);

        response.addCookie(cookie);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

cookie的练习

需求
- 显示商品浏览记录
开发步骤
- ①引入thymeleaf运行环境
  - 引入thymeleaf相关jar包
  - 在web.xml中，配置视图前缀、视图后缀
  - 引入ViewBaseServlet
  - 引入ModelBaseServlet
- ②编写shopping.html
  - 展示商品列表
- ③编写ShoppingServlet
  - addShoppingHistory : 添加商品浏览记录
  - showShoppingHistory : 获取商品浏览记录
- ④编写shopping_history.html
  - 展示商品浏览记录
②编写shopping.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>商品列表</title>
</head>
<body>

<a th:href="@{/shopping(method=addShoppingHistory,id=0)}">西游记</a><br>
<a th:href="@{/shopping(method=addShoppingHistory,id=1)}">红楼梦</a><br>
<a th:href="@{/shopping(method=addShoppingHistory,id=2)}">水浒传</a><br>
<a th:href="@{/shopping(method=addShoppingHistory,id=3)}">三国演义</a><br>


<a th:href="@{/shopping(method=showShoppingHistory)}">查看浏览记录</a>

</body>
</html>

③编写ShoppingServlet

@WebServlet("/shopping")
public class ShoppingServlet extends ModelBaseServlet {


    /**
     * 转发到shopping.html
     *
     * @param request
     * @param response
     */
    public void toShoppingPage(HttpServletRequest request, HttpServletResponse response) {
        System.out.println("toShoppingPage");
        try {
            processTemplate("shopping", request, response);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 添加商品浏览记录
     *
     * @param request
     * @param response
     */
    public void addShoppingHistory(HttpServletRequest request, HttpServletResponse response) {
        System.out.println("addShoppingHistory");
        String id = request.getParameter("id");
        System.out.println("id = " + id);
        //①判断是否是第一次请求
        Cookie historyCookie = null;//记录自己的Cookie
        Cookie[] cookies = request.getCookies();
        if (null != cookies && 0 != cookies.length) {
            for (Cookie cookie : cookies) {
                if ("history".equals(cookie.getName())) {
                    historyCookie = cookie;
                }
            }
        }
        if (null == historyCookie) {
            //是第一次请求
            historyCookie = new Cookie("history", id);
        } else {
            //不是第一次请求，判断商品之前是否有浏览过?
            //获取上一次浏览记录
            String historyStr = historyCookie.getValue();
            if (!historyStr.contains(id)) {
                //没有浏览过该商品，直接拼接
                historyStr = historyStr + "-" + id;
            } else {
                //有浏览过该商品，不处理
            }
            historyCookie.setValue(historyStr);

        }
        //将新的cookie返回给浏览器保存
        response.addCookie(historyCookie);

        //添加浏览记录完成之后，要展示浏览记录 (重定向)
        try {
            response.sendRedirect(request.getContextPath() + File.separator + request.getServletPath() + "?method=showShoppingHistory");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    /**
     * 展示商品浏览记录
     *
     * @param request
     * @param response
     */
    public void showShoppingHistory(HttpServletRequest request, HttpServletResponse response) {

        System.out.println("showShoppingHistory");
        String[] shoppingNames = {"西游记", "红楼梦", "水浒传", "三国演义"};
        //获取所有的商品浏览记录(cookie(name=history))
        Cookie historyCookie = null;
        Cookie[] cookies = request.getCookies();
        if (null != cookies && 0 != cookies.length) {
            for (Cookie cookie : cookies) {
                if ("history".equals(cookie.getName())) {
                    historyCookie = cookie;
                }
            }
        }

        List<String> list = new ArrayList<>();
        if (null == historyCookie) {
            //没有浏览记录
        } else {
            //有浏览记录 : 0-1-2-3
            String historyStr = historyCookie.getValue();
            String[] historyIndexs = historyStr.split("-");
            for (String historyIndex : historyIndexs) {
                String shoppingName = shoppingNames[Integer.parseInt(historyIndex)];
                list.add(shoppingName);
            }
        }

        request.setAttribute("list", list);
        try {
            processTemplate("shopping_history", request, response);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }


}

④编写shopping_history.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>商品浏览记录</title>
</head>
<body>

<div th:if="${list == null || #lists.size(list) == 0}">
    没有商品浏览记录
</div>

<div th:if="${!(list == null || #lists.size(list) == 0)}">
    <ul>

        <li th:each="history : ${list}" th:text="${history}">

        </li>
    </ul>
</div>

</body>
</html>

CookieUtils工具类

代码实现

public class CookieUtils {

    public static Cookie getCookie(Cookie[] cookies, String cookieName) {
        if (null == cookies || 0 == cookies.length) {
            return null;
        }
        for (Cookie cookie : cookies) {
            if (cookieName.equals(cookie.getName())) {
                return cookie;
            }
        }
        return null;
    }

}

session介绍

概述
- 服务器端会话技术；
- 只不过在浏览器端保存的是一个特殊标识，而共享的数据保存到了服务器端的内存对象中。每次请求时，浏览器都会将特殊标识携带到服务器端，根据这个标识来找到对应的内存空间，从而实现共享。
- 是一个域对象
域对象
- ServletRequest ：当前请求
- HttpSession ：当前会话
- ServletContext : 当前项目

session基本使用

代码实现

@WebServlet("/demo08")
public class Demo08Servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        String msg = "helloworld";
        session.setAttribute("msg",msg);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

@WebServlet("/demo09")
public class Demo09Servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        Object msg = session.getAttribute("msg");
        System.out.println("msg = " + msg);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

@WebServlet("/demo10")
public class Demo10Servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        session.removeAttribute("msg");
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

session执行流程

执行流程

①浏览器发起第一次请求Demo08Servlet
- 创建了一个session对象(9AA02B1B81450DAEBF01023CAF56DC19)
- 通过响应头Set-Cookie(JSESSIONID=9AA02B1B81450DAEBF01023CAF56DC19)携带到浏览器，并保存
②浏览器发起第二次请求Demo09Servlet
- 通过请求头Cookie(JSESSIONID=9AA02B1B81450DAEBF01023CAF56DC19)携带到服务器，
- 服务器根据JSESSIONID在服务器容器中找对应JSESSIONID的session对象
  - 如果有，直接使用
  - 如果没有，就创建新的session对象
③浏览器发起第三次请求Demo10Servlet
- 通过请求头Cookie(JSESSIONID=9AA02B1B81450DAEBF01023CAF56DC19)携带到服务器，
- 服务器根据JSESSIONID在服务器容器中找对应JSESSIONID的session对象
  - 如果有，直接使用
  - 如果没有，就创建新的session对象

sessoin相关配置

存活时长

<!-- ==================== Default Session Configuration ================= -->
<!-- You can set the default session timeout (in minutes) for all newly   -->
<!-- created sessions by modifying the value below.                       -->
<session-config>
    <session-timeout>30</session-timeout>
</session-config>

session默认存活时长为30分钟

@WebServlet("/demo08")
public class Demo08Servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        System.out.println(session.getId());
        session.setMaxInactiveInterval(5);
        String msg = "helloworld";
        session.setAttribute("msg",msg);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}