JavaWeb用户信息管理系统-创建登录业务的Filter

/**
 * 判断当前游览器是否登录的Filter
 *
 * */
@WebFilter(urlPatterns = {"*.do","*.jsp"})
public class UserLoginFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request=(HttpServletRequest)servletRequest;
        String uri=request.getRequestURI();
        //判断当前请求是否为login.jsp或者login.do，那么就放行
        if(uri.indexOf("login.jsp")!=-1||uri.indexOf("login.do")!=-1){
   filterChain.doFilter(servletRequest,servletResponse);
        }else{
            HttpSession session=request.getSession();
            Users users = (Users) session.getAttribute(Constants.USER_SESSION_KEY);
        if(users!=null){
            filterChain.doFilter(servletRequest,servletResponse);
        }else
        {
            request.setAttribute(Constants.REQUEST_MSG,"不登录休想访问");
            request.getRequestDispatcher("login.jsp").forward(servletRequest,servletResponse);
        }
        }
    }
    @Override
    public void destroy() {
    }
}