JavaWeb11-HTML篇笔记

1.1 案例二：记录用户的商品浏览记录:1.1.1 需求:
在购物网站上浏览商品的信息,商家为了留住用户,记住之前浏览的一些商品.

1.1.2 分析:1.1.2.1 技术分析:
1.1.2.2 步骤分析:
【步骤一】：在登录完成后，显示商品列表页面.
【步骤二】：为商品列表页面做一些准备工作.
【步骤三】：点击某个商品,将商品ID传递一个Servlet.
【步骤四】：在Servlet中:判断是否是第一次浏览商品
【步骤五】：如果是第一次：将商品的ID存入到Cookie中即可.
【步骤六】：如果不是第一次：判断该商品是否已经浏览了.
【步骤七】：如果浏览器过.删除之前元素,将该元素添加到最前面.
【步骤八】：如果没有浏览过该商品.判断最大长度，没有超过限制,直接加到最前,如果已经超过限制,删除最后一个，将其插入到最前.
1.1.3 代码实现:

public class ProductServlet extends HttpServlet {        private static final long serialVersionUID = 1L;        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {                /**                 * * 接收商品id.                 * * 接收从客户端带过来的所有Cookie.                 * * 从Cookie的数组中查找指定名称的Cookie.                 * * 判断是否是第一次浏览商品:                 *     * 第一次浏览商品                 *        * 直接将商品的ID存入到Cookie.                 *        * 将Cookie回写到浏览器.                 *     * 不是第一次浏览商品 1-2                 *        * 判断当前的商品是否已经在浏览记录.                 *            * 已经存在: 2-1 移除当前元素，将当前元素添加到最开始.                 *            * 没在浏览记录中:                 *                * 判断是否已经超过了最大长度:如果超过 2-1-3:删除最后一个 将当前元素添加到最前面.                 *                * 没有超过:直接将该元素添加到最前位置.                 *        * 将转换的id的值存入到Cookie,回写浏览器.                 */                // 接收id:                String id = request.getParameter("id");                // 获得所有的Cookie的信息:                Cookie[] cookies = request.getCookies();                // 判断是否是第一次:                Cookie cookie = CookieUtils.findCookie(cookies, "history");                if(cookie == null){                        // 第一次浏览商品                        Cookie c = new Cookie("history",id);                        c.setPath("/day11");                        c.setMaxAge(60*60*24*7);                        response.addCookie(c);                }else{                        // 不是第一次浏览                        // 判断选择的商品是否已经在浏览记录中 2-1                        String value = cookie.getValue();                        String[] ids = value.split("-");                        // 将数组变为集合：                        LinkedList<String> list = new LinkedList<String>(Arrays.asList(ids));                        if(list.contains(id)){                                // 之前浏览过该商品                                list.remove(id); // 1-2-3                                list.addFirst(id);                        }else{                                // 没有浏览过该商品.                                if(list.size() >=3 ){                                        // 超过3个                                        list.removeLast();                                        list.addFirst(id);                                }else{                                        // 没到3个.                                        list.addFirst(id);                                }                        }                        // 将list中的元素取出,使用-连接上保存到Cookie,写回浏览器.                        StringBuffer sb = new StringBuffer();                        for(String s:list){                                sb.append(s).append("-");                        }                        String sValue = sb.toString().substring(0,sb.length()-1);                        System.out.println(sValue);                        // 存入到Cookie中                        Cookie c = new Cookie("history",sValue);                        c.setPath("/day11");                        c.setMaxAge(60*60*24*7);                        response.addCookie(c);                }                request.getRequestDispatcher("/demo2/product_info.htm").forward(request, response);        }        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {                doGet(request, response);        }}1.1.4 总结:1.1.4.1 清空浏览记录:删除持久性的Cookie:public class ClearServlet extends HttpServlet {        private static final long serialVersionUID = 1L;        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {                Cookie cookie = new Cookie("history",null);                cookie.setPath("/day11");                cookie.setMaxAge(0);                response.addCookie(cookie);                response.sendRedirect("/day11/demo2/product_list.jsp");        }        /**         * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)         */        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {                // TODO Auto-generated method stub                doGet(request, response);        }