@WebServlet(name = "homepageServlet", urlPatterns = "/homepage")
public class HomePageServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Cookie[] cookies = req.getCookies();
        for (Cookie cookie : cookies) {
            if (!cookie.getName().equals("username")) {
                // 如果用戶是第一次訪問個人主頁，就通知瀏覽器跳轉(zhuǎn)到登陸頁面進(jìn)行登錄
                resp.sendRedirect(req.getContextPath() + "/login.jsp");
            }
        }
    }

}

@WebServlet(name = "loginServlet", urlPatterns = "/login")
public class LoginServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 獲取http請求參數(shù)username
        String username = request.getParameter("username");
        // 設(shè)置響應(yīng)內(nèi)容的類型
        response.setContentType("text/html;charset=utf-8");
        // 獲取Cookie值
        Cookie[] cookies = request.getCookies();
        for (Cookie cookie : cookies) {
            if (!cookie.getName().equals("username")) { // 用戶第一次訪問
                Cookie userCookie = new Cookie("username", username);
                userCookie.setMaxAge(300);
                response.addCookie(userCookie);
            }
            response.sendRedirect(request.getContextPath() + "/homepage.jsp");
        }
    }

}