使用Tomcat的过滤器验证用户是否登陆

Java菜鸟一枚，这两天一直被一个问题困扰，就是用tomcat的过滤器去验证用户是否登陆了。前一段时间一直犯了一个低级错误，导致我这两天这个功能一直没有试验成功！
那就是我把登陆页面放在了WEB-INF下面，因为犯晕，一直忘了WEB-INF就是保护自身资源，必须时tomcat自己返回的！希望后来者引以为戒！
那下面就把这个简单的登陆过滤器给大家看看吧
public class SessionCheck implements Filter{

public void init(FilterConfig filterConfig) throws ServletException {

}

public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
// 获得在下面代码中要用的request,response,session对象
HttpServletRequest request = (HttpServletRequest) servletRequest;
HttpServletResponse response = (HttpServletResponse) servletResponse;
HttpSession session = request.getSession();
System.out.println(request.getRequestURI());
//防止js,css，图片别过滤掉
if(request.getServletPath().endsWith(".css") || request.getServletPath().endsWith(".js") || request.getServletPath().endsWith(".png")){
filterChain.doFilter(request, response);
return;
}
if(session!=null&&session.getAttribute("admin")!=null) {
System.out.println(session.getAttribute("admin"));
filterChain.doFilter(request, response);
//logo.jsp一定要放在和WEB-INF平级的目录中
}else if(request.getRequestURI().equals(request.getContextPath()+"/login.jsp") || request.getRequestURI().equals("/login.do")){
filterChain.doFilter(request, response);
} else {
response.sendRedirect(request.getContextPath() + "/login.jsp");
}
}

public void destroy() {

}