登录失败不能出现提示框
@RequestMapping("/loginuser")
public String login(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException{
HttpSession httpsession = request.getSession();
httpsession.invalidate();
String username = request.getParameter("username");
String password = request.getParameter("password");
User user=new User();
//调用login方法来验证是否是注册用户
boolean loginType = SpsService.userlogin(username,password);
response.setContentType("text/html");
if(username=="")
{PrintWriter out1 = response.getWriter();
out1.println("<script language='javascript'>alert('用户名没有输入,请重新登陆');window.location.href='../login.jsp';</script>");}
为什么我在登录的时候没有输入用户名没有提示框出现啊?