protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		String username = request.getParameter("username");//获取页面传过来的参数
		String password = request.getParameter("password");
		//登录操作
		boolean flag = userBiz.checkLogin(username, password);
		
		if(flag) {
			request.getSession().setAttribute("loginuser", username);
//			response.sendRedirect("main.jsp");
			response.sendRedirect("SearchServlet");	//首页直接显示
		} else {//登录失败
			response.setContentType("text/html;charset=utf-8");
//			response.setCharacterEncoding("utf-8");
			PrintWriter out = response.getWriter();
			out.println("<script type='text/javascript'>");
			out.println("alert(\"登录失败！请重新登录\")");//反斜杠转义
			out.println("open(\"login.jsp\", \"_self\");");//重新打开新的页面, _self在原窗口打开
			out.println("</script>");
			out.close();
		}
	}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		request.setCharacterEncoding("utf-8");

		String currentPage = request.getParameter("currentPage");//获取当前页
		int no = currentPage == null?1:Integer.parseInt(currentPage);//如果当前页为空，则默认为1，否则转化为相应的int
		
//		String currentSearchPage = request.getParameter("currentSearchPage");
		String bookname = request.getParameter("keywords");//获取你输入的书名		
		List<Book> books = null;
		if(bookname==null || bookname.equals("")){
			books=bookbiz.findAll(3, no);//查询所有。3：代表每页显示的条数，no：当前显示页面
			request.setAttribute("totalPage", (bookbiz.count()/3 + 1));//将总页面数存入request
			
		} else {
			books = bookbiz.findBookByName(bookname,3, no);//根据书名模糊查询出数据
			System.out.println(books.size());
			request.setAttribute("totalPage", (books.size()/3 + 1));//将总页面数存入request
		}
		
		request.setAttribute("books", books);//将查询出的数据存入request
		request.setAttribute("current", no);//将当前页存入request	
		request.getRequestDispatcher("main.jsp").forward(request, response);//页面转发	
}

if(oneStock > 0) {//如果库存大于0
				//查看当前图书是否已经存在于购物车中
				//查看购物车列表是否已经存在该图书，对比两个图书id
				for (int j = 0; j < bookcart.size(); j++) {
					Book existBook = (Book) bookcart.get(j);
					if(existBook.getBid() == bid) {//如果购物车中的id==被选中的图书id，则购物车中的数量+1
						bookcart.remove(j);
						existBook.setCount(existBook.getCount()+1);//购物车中商品数量+1
						double totalPrice = existBook.getPrice();
						bookcart.add(existBook);//商品总价
						System.out.println("总价"+totalPrice);
						isNotExists = false;
						
						//修改库存
						isOrNotChangeStock = bookbiz.changeStock(bid, "-1");
						break;
					}
				}
				
				if(!isNotExists) {
					continue;
				}
				book.setBid(bid);
				
				//判断当前获取的图书信息是否为指定bid下的信息
				for (int j = 0; j < title.length; j++) {
//					request.setCharacterEncoding("utf-8");
					//解决页面图书标题中文显示乱码
					String title_temp =new String(title[j].getBytes("ISO-8859-1"),"utf-8");//取标题
					
					if(title_temp.indexOf(bids[i]+":")<0) {//indexOf匹配bids是否包含在title_temp中，如果没有返回-1
						continue;
					}
					if(image[j].indexOf(bids[i]+":")<0) {
						continue;
					}
					if(price[j].indexOf(bids[i]+":")<0) {
						continue;
					}
					if(stock[j].indexOf(bids[i]+":")<0) {
						continue;
					}
					//添加指定bid下的图书信息
					book.setBookname(filter(title_temp, bids[i]));
					book.setImage(filter(image[j], bids[i]));
					book.setPrice(Double.parseDouble(filter(price[j], bids[i])));
//						book.setPrice(Double.valueOf(filter(price[j], bids[i])));
					book.setStock(filter(stock[j], bids[i]));
					book.setCount(1);
					
					//修改库存
					bookbiz.changeStock(bid, "-1");
					bookcart.add(book);				
				}	
				
			}

protected void remove(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//1.获取图书id
		String bid = request.getParameter("bid");
		//2.获取购物车
		List<Book> bookcart = (List<Book>) request.getSession().getAttribute("bookcart");
		//3.循环查找购物车中相同的图书id
		for(int i = 0; i< bookcart.size(); i++) {
			Book book = bookcart.get(i);
			if(Integer.valueOf(bid) == book.getBid()) {
				//4.移除图书
				bookcart.remove(i);
				//5.修改库存
				bookbiz.changeStock(Integer.parseInt(bid), book.getCount()+"");
				break;
			}
		}		
		
		//6.将购物车保存到session中
//		request.getSession().setAttribute("bookcart", bookcart);
		request.getSession().setAttribute("bookcart_count", bookcart.size());
		System.out.println(request.getSession().getAttribute("bookcart_count"));
	}

String action = request.getParameter("action");
if(action.equals("update")) {
    updateCart(request, response);
}
else if(action.equals("remove")) {
    remove(request, response);
}

protected void updateCart(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//1.获取图书id和修改后的数量
		String bid = request.getParameter("bid");
		String count = request.getParameter("count");
		//2.获取购物车
		List<Book> bookcart = (List<Book>) request.getSession().getAttribute("bookcart");
		//3.查找购物车中修改过的图书，并修改相应的信息
		for (Book book : bookcart) {
			if(Integer.valueOf(bid) == book.getBid()) {
				//4.获取修改前的图书数量
				int old_count = book.getCount();
				//5.设置当前图书的新数量
				book.setCount(Integer.valueOf(count));
				System.out.println("当前图书新数量"+count);
				
				int nowStock = 0;
				try {
					nowStock = basedao.queryStock(Integer.parseInt(bid));
				} catch (Exception e) {
					e.printStackTrace();
				} 
				
				//6.修改库存
				bookbiz.changeStock(Integer.parseInt(bid), (old_count-Integer.parseInt(count))+"");
				break;			
			}
		}
	}

<%--用户退出登录 --%>
<%
	request.getSession().removeAttribute("loginuser");
	request.getSession().removeAttribute("bookcart");
	request.getSession().removeAttribute("bookcart_count");
	response.sendRedirect("login.jsp");
%>

if(oneStock > 0) {//如果库存大于0
	//...
}