今天做一个过滤器，碰上页面重定向循环的情况：
浏览器的访问路径是：http://192.168.16.104:8080/biologyInfo/login/login/login/login/login/login/login/login/login/login/login/login/login/login/login/login/login/login/login/login/login/login/login1.htmls
过滤器的类如下：
1 package com.agen.util; 2 3 import java.io.IOException; 4 5 import javax.servlet.Filter; 6 import javax.servlet.FilterChain; 7 import javax.servlet.FilterConfig; 8 import javax.servlet.ServletException; 9 import javax.servlet.ServletRequest; 10 import javax.servlet.ServletResponse; 11 import javax.servlet.http.HttpServletRequest; 12 import javax.servlet.http.HttpServletResponse; 13 import javax.servlet.http.HttpSession; 14 15 import org.springframework.util.Assert; 16 import org.springframework.util.StringUtils; 17 18 import com.agen.entity.User; 19 20 /** 21 * 首先写一个登录权限过滤类--LoginFilter类实现Filter接口 22 * @author 申旭栋 23 *下面这三个方法是必须要实现的 24 */ 25 public class LoginFilter implements Filter { 26 27 @Override 28 public void init(FilterConfig filterConfig) throws ServletException { 29 // TODO Auto-generated method stub 30 31 } 32 33 34 @Override 35 public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException { 36 // 获得在下面代码中要用的request,response,session对象 37 HttpServletRequest servletRequest = (HttpServletRequest) request; 38 HttpServletResponse servletResponse = (HttpServletResponse) response; 39 HttpSession session = servletRequest.getSession(); 40 41 // 获得用户请求的URI 42 String path = servletRequest.getRequestURI(); 43 44 // 从session里取用户的登陆ID 45 User user = (User) session.getAttribute("user"); 46 47 // 登陆页面无需过滤 48 if("/biologyInfo/".equals(path) || "/biologyInfo/login/login1.htmls".equals(path)) { 49 chain.doFilter(servletRequest, servletResponse); 50 return; 51 } 52 53 // 判断如果没有取到员工信息,就跳转到登陆页面 StringUtils.isEmpty(username)等价于username == null || "".equals(username) 54 if (user == null) { 55 // 跳转到登陆页面 56 servletResponse.sendRedirect("login/login1.htmls"); 57 } else { 58 // 已经登陆,继续此次请求 59 chain.doFilter(request, response); 60 } 61 62 } 63 64 @Override 65 public void destroy() { 66 // TODO Auto-generated method stub 67 68 } 69 70 }