防止未登录访问 可用过滤器Filter实现

在做开发时，遇到 防止未登录访问时需要自定义过滤器访问。在开发过成中遇到的问题有：

1.、死循环（解决办法：一定要对重定向的URL做判断）

2、过滤完之后的页面是空白显示（解决办法：忘记加doFilter了，加上doFilter之后问题可以解决）

java代码

package com.zh.util;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;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;import com.zh.bean.admin.Admin;public class SessionFilter implements Filter{@Overridepublic void destroy() {}@Overridepublic void doFilter(ServletRequest arg0, ServletResponse arg1,FilterChain arg2) throws IOException, ServletException {System.out.println("do!!");HttpServletRequest request = (HttpServletRequest)arg0;HttpServletResponse response = (HttpServletResponse)arg1;String url = request.getRequestURI();System.out.println(url);boolean b1=!url.equals("/cpShop/admin/login.jsp");boolean b2=url.substring(url.length()-3).equals(".do");boolean b3=!url.substring(url.length()-13).equals("loginAdmin.do");boolean b4=!url.substring(url.length()-4).equals(".jsp");HttpSession session = request.getSession();Admin admin = (Admin) session.getAttribute("admin");System.out.println(admin+"  ");if(b1&&b2&&b3&&b4){if(admin == null){System.out.println("8888888888");response.sendRedirect("/cpShop/admin/login.jsp");}else{arg2.doFilter(request, response); return; }}else{arg2.doFilter(request, response); return; }}@Overridepublic void init(FilterConfig arg0) throws ServletException {System.out.println("start!!");}}

web.xml配置文件中的代码

<filter><description>过滤器</description><filter-name>adminFilter</filter-name><filter-class>com.zh.util.SessionFilter</filter-class></filter><filter-mapping><filter-name>adminFilter</filter-name><url-pattern>/admin/*</url-pattern></filter-mapping>