【LoginServlet】
@WebServlet(name="loginServlet",urlPatterns = "/login")public class LoginServlet extends HttpServlet{ private static final Map userDatabase = new Hashtable<>(); static { userDatabase.put("user1","123456"); userDatabase.put("user2","123456"); userDatabase.put("user3","123456"); userDatabase.put("user4","123456"); } @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { HttpSession session = req.getSession(); if (req.getParameter("logout")!=null){ session.invalidate(); resp.sendRedirect("login"); return; // 已经登录上的 }else if (session.getAttribute("username")!=null){ resp.sendRedirect("tickets"); return; } req.setAttribute("loginFailed",false); req.getRequestDispatcher("/WEB-INF/jsp/view/login.jsp").forward(req,resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { HttpSession session = req.getSession(); //注销 if (req.getParameter("logout")!=null){ session.invalidate(); resp.sendRedirect("login"); return; // 登录会话 }else if (session.getAttribute("username")!=null){ resp.sendRedirect("tickets"); return; } String username = req.getParameter("username"); String userpassword = req.getParameter("userpassword"); if (username == null || userpassword == null || !LoginServlet.userDatabase.containsKey(username)|| !userpassword.equals(LoginServlet.userDatabase.get(username))){ req.setAttribute("loginFailed",true); req.getRequestDispatcher("/WEB-INF/jsp/view/login.jsp") .forward(req,resp); }else { session.setAttribute("username",username); req.changeSessionId();//登录更新会话id resp.sendRedirect("tickets"); } }} 【重定向和转发】
转发是服务器行为。
重定向是客户端行为。
【login.jsp】
登录
<% if ((boolean)request.getAttribute("loginFailed")){ out.println("您输入的密码或用户名不对"); } %>