JavaWeb会话技术Session的简单使用

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    HttpSession session = req.getSession();
    PrintWriter writer = resp.getWriter();
    // 给session绑定一个user对象
    session.setAttribute("user", new User(1, "kongsam"));
    List users = new ArrayList<>();
    users.add("kongsam");
    users.add("xiaoming");
    users.add("xiaohong");
    // 给session绑定一个list数组
    session.setAttribute("list", users);
    // 最后打印输出
    writer.println("JSESSIOnID= " + session.getId());
    writer.println("object => user = " + session.getAttribute("user").toString());
    for (String user : users) {
        writer.println("list => user = " + user);
    }
}

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    HttpSession session = req.getSession();
    // 创建一个假数据库
    Map vipUsers = new HashMap<>();
    vipUsers.put("kongsam", new VipUser(1, "kongsam", "123", 50));
    vipUsers.put("xiaoming", new VipUser(2, "xiaoming", "123", 100));
    vipUsers.put("xiaohong", new VipUser(3, "xiaohong", "123", 200));
    // 将假数据库的数据存放到Session中
    session.setAttribute("vipUsers", vipUsers);
}

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    req.setCharacterEncoding("utf-8");
    resp.setCharacterEncoding("utf-8");
    resp.setContentType("text/html;charset=utf-8");
    HttpSession session = req.getSession();
    // 获取username
    String username = req.getParameter("username");
    // 从Session中取出数据库
    Map maps = (Map) session.getAttribute("vipUsers");
    // 判断数据库中是否有和username匹配的用户
    if (maps.get(username) != null && maps.get(username).getUsername().equals(username)) {
        resp.getWriter().println(maps.get(username).getUsername() + "您好，您目前的积分是: " + maps.get(username).getPoints());
    } else {
        resp.getWriter().println("您还没有办理会员卡，前台正在为您办理中...，请刷新页面。");
        maps.put(username, new VipUser(1, username, "123", 50));
        session.setAttribute("vipUsers", maps);
    }
}