頁面訪問被攔截，j2ee中如何攔截jsp頁面？

public class RightFilter implements Filter {public void init(FilterConfig filterConfig) throws ServletException {}public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,FilterChain filterChain) throws IOException, ServletException {HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;HttpServletResponse httpServletResponse = (HttpServletResponse) servletResponse;User user = (User) httpServletRequest.getSession(true).getAttribute("user");if (!isExcludePages(httpServletRequest.getRequestURI())) {if (user == null) {httpServletResponse.sendRedirect(httpServletRequest.getContextPath() + "/login.jsp");return;}}filterChain.doFilter(servletRequest, servletResponse);}private boolean isExcludePages(String url) {return url.indexOf("login.dhtml") != -1|| url.indexOf("logout.dhtml") != -1|| url.indexOf("login.jsp") != -1|| url.endsWith(".css")|| url.endsWith(".js")|| url.endsWith(".gif")|| url.endsWith(".jpg")|| url.endsWith(".png");}public void destroy() {}
}

<filter><filter-name>rightFilter</filter-name> <filter-class>com.xxx.filter.RightFilter</filter-class> </filter><filter-mapping><filter-name>rightFilter</filter-name><url-pattern>*.dhtml</url-pattern></filter-mapping>