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() + "
");		out.write(book.getName() + "
");		out.write(book.getAuthor() + "
");		out.write(book.getDescription() + "
");		// 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
    
      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);			}		}				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);	}}