通过TOMCAT把系统启动，可以正常登陆门户，登陆进去选择子系统的时候点击登陆的时候，可是去又回到了登陆界面，如此反复就是不能够进入子系统，查看后台报的错误：
Cannot forward after response has been committed
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username = request.getParameter("username");
String password = request.getParameter("password");
User user = new User(username, password);
if (userService.checkUser(user)) {
request.getRequestDispatcher("/normal/main.jsp").forward(request, response);
return;//单独添加...
}
request.setAttribute("err", "用户名或者密码错误");
request.getRequestDispatcher("/normal/login.jsp").forward(request, response);
return;
}
