1. 用户上次访问时间(LastAccessServlet01_du)
Cookie[] cookies = request.getCookies();
if ("lastAccess".equals(cookies[i].getName()));cookies[i].getValue();
Cookie cookie = new Cookie("lastAccess", new Date().toLocaleString());
response.addCookie(cookie);
2. 实现图书购物车(ListBookServlet02_du)
PurchaseServlet02_du.java 所选图书加入购物车
List cart = (List) session.getAttribute("cart");
if (cart == null) {
// 首次购买，为用户创建一个购物车(List集合模拟购物车)
cart = new ArrayList();
// 将购物城存入Session对象
session.setAttribute("cart", cart);
}
// 将商品放入购物车
cart.add(book);
// 创建Cookie存放Session的标识号
Cookie cookie = new Cookie("JSESSIONID", session.getId());
cookie.setMaxAge(60 * 30);
cookie.setPath("/ch06_du");
resp.addCookie(cookie);
1. <form action="/ch06_du/LoginServlet03_du" method="post">
2. String username = request.getParameter("username");
String password = request.getParameter("password");
PrintWriter pw = response.getWriter();
//假设正确的用户名 是dzjiang 密码是123456
if (("dzjiang").equals(username) && ("123456").equals(password)) {
User03_du user = new User03_du();
user.setUsername(username);
user.setPassword(password);
request.getSession().setAttribute("user", user);
response.sendRedirect("/ch06_du/IndexServlet03_du");
} else {
pw.write("用户名或密码错误，登录失败");
response.setHeader("Refresh","3;URL=/ch06_du/Login03_du.html");
//response.sendRedirect("/ch06_du/Login03_du.html");
}
3. HttpSession session = request.getSession();
User03_du user = (User03_du) session.getAttribute("user");
if (user == null) {
response.getWriter().print(
"您还没有登录，请登录");
} else {
response.getWriter().print("您已登录，欢迎你，" + user.getUsername() + "！");
response.getWriter().print(
"退出");
// 创建Cookie存放Session的标识号
Cookie cookie = new Cookie("JSESSIONID", session.getId());
cookie.setMaxAge(60 * 30);
cookie.setPath("/ch06_du/03");
response.addCookie(cookie);
}
4. // 将Session对象中的User对象移除
request.getSession().removeAttribute("user");
response.sendRedirect("/ch06_du/IndexServlet03_du");
//创建内存图象并获得其图形上下文
BufferedImage image =
new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
char [] rands = generateCheckCode(); //产生随机的认证码
drawBackground(g); //产生背景图像
drawRands(g,rands);
g.dispose(); //结束图像的绘制过程，完成图像
//将图像输出到客户端
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ImageIO.write(image, "JPEG", bos);
byte [] buf = bos.toByteArray();
response.setContentLength(buf.length);
//下面的语句也可写成：bos.writeTo(sos);
sos.write(buf);
bos.close();
sos.close();
//将当前验证码存入到Session中
session.setAttribute("check_code",new String(rands));
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