登录验证后端添加过滤器

public class Filter implements javax.servlet.Filter {  
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException 
{      
//强制转换    
HttpServletRequest request = (HttpServletRequest) req;     
//获取请求地址    
String uri = request.getRequestURI();        /*判断请求地址是否带有登陆资源       
* 如果有,直接放行      
* 如果没有,判断是否登录   
* 如果登陆了,直接转发到相应的资源,  
* 如果没有登录,转发到登录提示还没登录*/  
if (uri.equals("/Servlet") || uri.equals("/")||uri.contains("/index.jsp") || uri.contains("/CheckcodeServlet") || 
uri.contains("/css/") || uri.contains("/js/")) {         
chain.doFilter(req, resp);     
} else {        
Object name = request.getSession().getAttribute("username");  if (name != null) {          
chain.doFilter(req, resp);     
} else {     
request.setAttribute("loginmsg", "您还没有登录");                request.getRequestDispatcher("index.jsp").forward(req, resp);       
chain.doFilter(req, resp);      
}    
}  
}