servlet显示商品浏览历史记录

来源：互联网发布：数据库原理视频下载编辑：程序博客网时间：2024/05/21 10:52

假设有一个数据库和书本对象

//数据库class Db{private static Map<String, Book> map = new LinkedHashMap();static{map.put("1", new Book("1","web开发","老张"));map.put("2", new Book("2","spring","老毕"));map.put("3", new Book("3","struts","老张"));map.put("4", new Book("4","jdbc","老黎"));}//拿到书public static Map getAll(){return map;}}//书对象class Book{private String id;private String name;private String author;public Book() {super();}public Book(String id, String name, String author) {super();this.id = id;this.name = name;this.author = author;}public String getId() {return id;}public void setId(String id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getAuthor() {return author;}public void setAuthor(String author) {this.author = author;}}

第一个servlet显示商品列表和历史记录

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//设置防止乱码response.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=utf-8");//显示商品信息PrintWriter out = response.getWriter();out.write("有以下商品信息：<br>");Map<String, Book> map = Db.getAll();for(Map.Entry<String, Book> entry : map.entrySet()){Book book = entry.getValue();out.print("<a href='/day07/CookieDemo3?id="+book.getId()+"'target='_blank'> "+book.getName()+"</a><br>");}//显示用户曾经看过什么商品out.print("<br>您曾经看过如下商品：<br>");Cookie cookies[] = request.getCookies();for(int i=0; cookies!=null&&i<cookies.length; i++){if(cookies[i].getName().equals("bookHistory")){String ids[] = cookies[i].getValue().split("\\,");     //2,2,3for(String id : ids){Book book = (Book) Db.getAll().get(id);out.print(book.getName()+"<br>");}}}}

第二个servlet显示商品具体信息，存储cookie

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//设置防止乱码response.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=utf-8");//显示商品信息PrintWriter out = response.getWriter();//根据用户带来的id显示商品信息String id = request.getParameter("id");Book book = (Book) Db.getAll().get(id);out.print(book.getId()+"<br>");out.print(book.getName()+"<br>");out.print(book.getAuthor()+"<br>");//构建Cookie回写给浏览器String cookieValue = buildCookie(id,request);Cookie cookie = new Cookie("bookHistory", cookieValue);cookie.setPath("/day07");cookie.setMaxAge(3600*24);response.addCookie(cookie);}private String buildCookie(String id, HttpServletRequest request) {String bookHistory = null;Cookie cookies[] = request.getCookies();for(int i=0; cookies!=null&&i<cookies.length; i++){if(cookies[i].getName().equals("bookHistory")){bookHistory = cookies[i].getValue();}}/*分情况谈论  * old   id   now * null  1    1 * 2,3   1   1,2,3 * 1      1   1 *  ... */if(bookHistory==null){return id;}//LinkedList便于增删改查LinkedList list = new LinkedList(Arrays.asList(bookHistory.split("\\,")));if(list.contains(id)){list.remove(id);list.addFirst(id);}else{if(list.size()>=3){list.removeLast();list.addFirst(id);}else{list.addFirst(id);}}StringBuilder sb = new StringBuilder();for(Object ob : list){sb.append(ob+",");}return sb.deleteCharAt(sb.length()-1).toString();}

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