用户登录过滤的问题

web.xml：  <filter>
<filter-name>LoginFilter</filter-name>
<filter-class>
com.train.filter.LoginFilter
</filter-class>
<init-param>
<param-name>url</param-name>
<param-value>/login.jsp</param-value>
</init-param>
  </filter>
 <filter-mapping>
<filter-name>LoginFilter</filter-name>
<url-pattern>/*</url-pattern>
  </filter-mapping>Filter类：public class LoginFilter implements Filter{
String url="/";
@Override
public void destroy() {
// TODO Auto-generated method stub

} @Override
public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse res= (HttpServletResponse) response;
HttpSession session = req.getSession();
User user=(User) session.getAttribute("user");
if(user!=null){
chain.doFilter(req, res);
return;
}
else{
res.sendRedirect(req.getContextPath+url);
}
} @Override
public void init(FilterConfig filterConfig) throws ServletException {
url=filterConfig.getInitParameter("url");
}}当输路径时提示（此页面不能正确地重定向）我的页面一部分放在WebRoot下面还有一部分放在WebRoot下的admin文件夹内！全都需要登录过滤，大家帮帮忙！