session过期判断的基本思想：用户登录成功后，将用户账号信息保存在session中，然后几乎每次执行命令都要经过过滤器，过滤器检查session中是否存在账号，若不存在，
则返回登录页面，反之正常执行。
1、web.xml中添加
<filter><!-- 配置过滤器，用来检查session中是否存在用户登录账号信息 --> <filter-name>ChkSessionFilter</filter-name> <filter-class>com.um.core.filter.LoginFilter</filter-class> </filter> <filter-mapping> <filter-name>ChkSessionFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>
<!-- 配置session过期时间 -->
<session-config> <session-timeout>20</session-timeout> </session-config> <welcome-file-list>
2、fiter
package com.um.core.filter; 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.um.core.controller.BaseController; /** * 登录验证过滤器 */ public class LoginFilter extends BaseController implements Filter { /** * 初始化 */ public void init(FilterConfig fc) throws ServletException { // FileUtil.createDir("d:/FH/topic/"); } public void destroy() { } public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest) req; HttpServletResponse response = (HttpServletResponse) res; String[] notFilter = new String[] { "userLogin","js","xml","css","demo","img","images","fonts","common","gateway","payCallback","toOrderPage","show_order"};//过滤字段、路径。。。。。。 String urlPath = request.getServletPath(); Boolean flg = false; for (String url : notFilter) { if ((urlPath.contains(url))) { flg = true; } } if(flg){ chain.doFilter(req, res); }else{ HttpSession session = request.getSession(); String UID = (String) session.getAttribute("UID"); //登录成功将登录ID放入session中，这里将session取出对比 if (null == UID||"".equals(UID)) { logger.warn("用户登录超时或未登录，请重新登录！"); java.io.PrintWriter out = response.getWriter(); out.println("<html>"); out.println("<script>"); out.println("window.open ('"+request.getContextPath()+"/login.jsp','_top')"); out.println("</script>"); out.println("</html>"); return; }else { chain.doFilter(req, res); } } } }