<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"><display-name></display-name><!-- 编码过滤器 --><filter><filter-name>CharactorEncodingFilter</filter-name><filter-class>cn.happy.filter.CharacterEncodingFilter</filter-class></filter><!-- 鉴权过滤器 --><filter><filter-name>SessionFilter</filter-name><filter-class>cn.happy.filter.SessionFilter</filter-class><!-- 初始化参数 --><init-param><param-name>execuldeUrl</param-name><param-value>/servlet/(Login|Register)Servlet</param-value></init-param></filter><!-- 按照书写先后顺序  ，执行顺序按照Sevlet-Mapping 书写顺序 --><filter-mapping><filter-name>CharactorEncodingFilter</filter-name><url-pattern>/*</url-pattern></filter-mapping><!-- 需要权限的页面 --><filter-mapping><filter-name>SessionFilter</filter-name><url-pattern>/jsp/*</url-pattern></filter-mapping><filter-mapping><filter-name>SessionFilter</filter-name><url-pattern>/servlet/*</url-pattern></filter-mapping><servlet><description>This is the description of my J2EE component</description><display-name>This is the display name of my J2EE component</display-name><servlet-name>LoginServlet</servlet-name><servlet-class>cn.happy.servlet.LoginServlet</servlet-class></servlet><servlet-mapping><servlet-name>LoginServlet</servlet-name><url-pattern>/servlet/LoginServlet</url-pattern></servlet-mapping><welcome-file-list><welcome-file>index.jsp</welcome-file></welcome-file-list>
</web-app>

package cn.happy.filter;import java.io.IOException;
import java.util.regex.Pattern;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;public class SessionFilter implements Filter {Pattern patternUrl;//能从配置文件获取内容public void init(FilterConfig config) throws ServletException {String url=config.getInitParameter("execuldeUrl");  ///servlet/LoginServletif(url!=null&&!url.equals("")){ //配置了例外//为了获取到一个正则对象  patternUrl= Pattern.compile(url); //我们定制的正则规范 /servlet/LoginServlet}}public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {HttpServletRequest req=(HttpServletRequest)request;HttpServletResponse res=(HttpServletResponse)response;//路径中包含 /servlet/LoginServlet  方向String servletPath = req.getServletPath();System.out.println(servletPath+"===========================");if(patternUrl.matcher(servletPath).matches()){chain.doFilter(request, response);return;}Object sessionObj = req.getSession().getAttribute("uname");if(sessionObj!=null){  //证明用户已经登录了//放行chain.doFilter(request, response);}else{System.out.println("session filter not session data");//证明用户没有登录，返回到登录   /Jsp-Day05Filterres.sendRedirect(req.getContextPath()+"/login.jsp");}}public void destroy() {}}