Servlet跳转到jsp不加载css样式_idea中通过servlet跳转到jsp页面加载不到css文件

jsp向servlet作请求，servlet接受到请求之后转发会原来的jsp页面，出现jsp页面不加载css样式的现象

1.jsp页面请求代码

<script type="text/javascript">
	$(document).ready(function() {
		$("#submitbtn").click(function() {
			$("#loginform").attr("action","/BookStore/UserServlet?method=login")
			var uname = $("#username").val();
			var pwd = $("#password").val();
			if (uname == "") {
				alert("用户名不能为空");
				return false;
				
			}
			if (pwd == "") {
				alert("密码不能为空");
				return false;
			}
			$("#loginform").submit();
 
		});
	});
</script>

	public String login(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 
		User form = CommonUtils.toBean(req.getParameterMap(), User.class);
 
		Map<String, String> errors = new HashMap<String, String>();
		// 对验证码进行校验
		String sessionVerifyCode = (String) req.getSession().getAttribute("session_vcode");
		String verifyCode = form.getVerifyCode();//等同于req.getParameter("verifyCode");
		System.out.println("1."+sessionVerifyCode);
		System.out.println("2."+verifyCode);
		if (verifyCode == null || verifyCode.trim().isEmpty()) {
			errors.put("verifyCode", "验证码不能为空！");
		} else if (verifyCode.length() != 4) {
			errors.put("verifyCode", "验证码长度必须为4！");
		} else if (!verifyCode.equalsIgnoreCase(sessionVerifyCode)) {
			errors.put("verifyCode", "验证码错误！");
		}
 
		/*
		 * 判断map是否为空，不为空，说明存在错误
		 */
		if (errors != null && errors.size() > 0) {
			/*
			 * 1. 保存errors到request域 2. 保存form到request域，为了回显 3. 转发到regist.jsp
			 */
			req.setAttribute("errors", errors);
			req.setAttribute("user", form);
 
			return "f:/jsps/user/login.jsp";
			
		}
 
		try {
			User user = userService.login(form);
			req.getSession().setAttribute("session_user", user);
 
			return "r:/index.jsp";// session重定向到index.jsp
 
		} catch (Exception e) {
			req.setAttribute("msg", e.getMessage());
			req.setAttribute("form", form);
			return "f:/jsps/user/login.jsp";// 转发错误信息
		}
 
	}