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);

	}



}