编写FailServlet和SuccessServlet类

@WebServlet("/successServlet")
public class SuccessServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取request域中共享的user对象
User user = (User) request.getAttribute("user");

	        if(user != null){
	            //给页面写一句话
	
	            //设置编码
	            response.setContentType("text/html;charset=utf-8");
	            //输出
	            response.getWriter().write("登录成功！"+user.getUsername()+",欢迎您");
	        }

}
@WebServlet("/failServlet")
public class FailServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//给页面写一句话

	        //设置编码
	        response.setContentType("text/html;charset=utf-8");
	        //输出
	        response.getWriter().write("登录失败，用户名或密码错误");
	
	    }
	
	    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	        this.doPost(request,response);
	    }
	}