AJAX实现登陆

先添加点击事件

<input type="button" id="submitt"   value="立即登录" />

展示信息

<div id="showMsg" style="text-align: center"></div>

发送JSON格式数据给servlet，并接收回传信息

<script>
            submitt.onclick=function () {
                //alert(12212);
                $.post("/shop/login",
                    {
                        "username":$("#username").val(),
                        "password":password.value
                    },
                    function (data) {
                        if (data.code==111){
                            $("#showMsg").html("对不起，你输入的账号或者密码错误").css("color","red");
                        }else{
                            window.location.href="/shop/home";
                        }
                    });
            }

验证登陆，并将结果回传给jsp

@WebServlet("/login")
public class LoginServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        /*获取请求参数telephone，password*/
        String telephone = req.getParameter("username");
        String password = req.getParameter("password");
       //System.out.println(telephone+"-----"+password);
        /*调用dao，验证是否匹配*/
        ILoginDAO dao=new LoginDAOImpl();
        Map<String ,Object> user = dao.isLogin(telephone,password);

        resp.setContentType("text/json;charset=UTF-8");
        PrintWriter out = resp.getWriter();
        Map<Object, Object> map = new HashMap<>();

        if (user==null){
            /**如果不正确提示电话或者密码不正确*/
            map.put("code","111");
            map.put("error","对不起，你输入的账号或者密码错误");
            //req.setAttribute("error","对不起，你输入的账号或者密码错误");
            //req.getRequestDispatcher("/views/login.jsp").forward(req,resp);
        }else{
            /**如果正确,跳转到主页*/
            /*为什么用session，从共享数据开始到关闭浏览器，共享数据都可以获取，不受请求转发和重定向的影响*/
            HttpSession session = req.getSession();//获取session对象
            session.setAttribute("user",user);
            resp.sendRedirect("/shop/home");
        }
        String s = JSON.toJSONString(map);
        out.write(s);
        out.close();
    }
}