java_Cookies_1_商品浏览历史记录servlet2

public class CookiesServlet2 extends HttpServlet {// 显示商品详细信息public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setCharacterEncoding("UTF-8");response.setContentType("text/html;charset=UTF-8");PrintWriter out = response.getWriter();// 根据用户带过来的id，显示相应商品的详细信息String id = request.getParameter("id");Book book = (Book) Db.getAll().get(id);out.write(book.getId() + "<br/>");out.write(book.getName() + "<br/>");out.write(book.getAuthor() + "<br/>");out.write(book.getDescription() + "<br/>");// 构建Cooikes回写给浏览器String cookieValue = buildCookie(id, request);Cookie cookie = new Cookie("bookHistory", cookieValue);cookie.setMaxAge(1 * 30 * 24 * 60 * 60);cookie.setPath("/NANA");response.addCookie(cookie);}private String buildCookie(String id, HttpServletRequest request) {// if none cookie, bookHistory=null, cookie value =1// if contain cookie,bookHistory=2,5,1 return 1 2 5// cookieHistory=2,5,4 browns 1 return 1,2,5 到了列表最大值// cookieHistory=2,5 browns 1 return 1,2,5 没到最大值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();}}if (bookHistory == null) {return id;}LinkedList<String> list = new LinkedList<String>(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);}}StringBuffer sb = new StringBuffer();for(String bid:list){sb.append(bid+",");}return sb.deleteCharAt(sb.length()-1).toString();}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}