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);
	}

}