解决Filter对用户登录验证产生死循环

要对后台管理文件夹下的所有管理页面进行过滤，阻止未登录的用户访问这些页面，在操作中出现了重定向死循环，经过思考，最终找到了解决办法，现在把代码贴出来。

Filter过滤器类

package dsh.bikegis.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class LoginCheckFilter implements Filter {

	public void init(FilterConfig filterConfig) throws ServletException {
	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		HttpServletRequest req = (HttpServletRequest) request;
		HttpServletResponse res = (HttpServletResponse) response;
		HttpSession session = req.getSession(true);

		// 从session里取的用户名信息
		String username = (String) session.getAttribute("userName");
		String   uri   =   ((HttpServletRequest)   request).getRequestURI(); 
		// 判断如果没有取到用户信息,就跳转到登陆页面
		if (username != null || !("".equals(username))|| uri.endsWith("index.html") ) {
			
			chain.doFilter(request, response);
		} else {
			// 跳转到登陆页面
			RequestDispatcher dispatcher = request.getRequestDispatcher("index.html");  
			dispatcher.forward(request, response);  
			
		}
	}

	public void destroy() {
	}
}

 web.xml配置过滤器：<filter>

          <filter-name>yes</filter-name>  
          <filter-class>dsh.bikegis.filter.LoginCheckFilter</filter-class>  
      </filter>  
   
      <filter-mapping>  
          <filter-name>yes</filter-name>  
          <url-pattern>/manage/*</url-pattern>  
      </filter-mapping>  

 //登錄驗證

	public String loginUser(){
		if(this.us.getUser(user)!=null){
			 ActionContext.getContext().getSession().put("userName",user.getUsername());  
			return ActionSupport.SUCCESS;
		}
		this.errMesg="密碼或者用戶名錯誤，請重新輸入！";
		return ActionSupport.ERROR;
	}

 

其中登录验证为 struts2中的Action，前台登录页面访问这个Action，成功的话就把用户名放入session中；在Filter中获得session中存放的字符串，如果不为空，或者是登录页面（此处为index.html）的话则验证成功，就放行，让其具有访问manage目录下的所有文件。否则跳转到index.html