<filter-mapping>

        <filter-name>SessionFilter</filter-name>

        <url-pattern>/*</url-pattern>

        <dispatcher>REQUEST</dispatcher>

    </filter-mapping>

<filter>

    <filter-name>SessionFilter</filter-name>

    <!-- 拦截类 -->

    <filter-class>com.skin.generate.user.UserLoginFilter</filter-class>

    <init-param>

        <param-name>loginUrl</param-name>

        <param-value>/finder/login.html</param-value>

    </init-param>

    <!-- 配置参数 比如不拦截的路径 -->

    <init-param>

        <param-name>excludes</param-name>

        <param-value>

            /register.html,

            /resource/**/*,

            /note/**/*

        </param-value>

    </init-param>

</filter> 

package com.skin.generate.user;

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.Cookie;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

import com.skin.finder.security.UserSession;

import com.skin.finder.web.util.Client;

import com.skin.finder.web.util.CookieUtil;

import com.skin.generate.entity.User;

public class UserLoginFilter implements Filter {

/*

     * String nofilter; String nofilterFiles[]; String sendRedirect;

     */

    public void destroy() {

    }

    public void doFilter(ServletRequest req, ServletResponse res,

            FilterChain chain) throws IOException, ServletException {

        HttpServletRequest request = (HttpServletRequest) req;

        HttpServletResponse response = (HttpServletResponse) res;

        String path = request.getServletPath();

        String url = request.getRequestURI();

        // 如果不需要过滤的静态文件，直接放行

        if (path.endsWith(".css") || path.endsWith(".js")

                || path.endsWith("Login.html")

                || url.indexOf("resource") > 0 || url.indexOf("note") > 0

                || url.endsWith("login.jsp") || path.endsWith(".gif")

                || path.endsWith(".ico")) {

            chain.doFilter(request, response);

            return;

        } else {

            if (checkUser(request, response)) {

                chain.doFilter(request, response);// 如果用户已经登录，就放行

                return;

            } else {

                // 没有登录，重定向到登录页面

                String contextPath = getContextPath(request);

                response.sendRedirect(contextPath+ "/template/finder/login.jsp");

                return;

            }

        }

    }

    protected String getContextPath(HttpServletRequest request) {

        String contextPath = request.getContextPath();

        if ((contextPath == null) || (contextPath.equals("/"))) {

            return "";

        }

        return contextPath;

    }

    private boolean isInArray(String path, String nofilterFiles[]) {

        for (int i = 0; i < nofilterFiles.length; i++) {

            String nofilterFile = nofilterFiles[i];

            if (nofilterFile.equals(path)) {

                return true;

            }

        }

        return false;

    }

    private boolean checkUser(HttpServletRequest request,

            HttpServletResponse response) throws IOException {

        //1.判断cookie 是否存在

        Cookie cookie = CookieUtil.getCookie(request, Client.COOKIE_NAME);

        if(cookie ==null ){

            return false;

        }

        //2.校验session

        HttpSession session = request.getSession(false);// 如果不存在返回空

        if (session == null) {

            return false;

        }

        //3.校验登录用户

        Object obj = session.getAttribute(SessionUtils.USER_NAME);

        if (obj == null) {

            return false;

        }

        return true;

    }

    public void init(FilterConfig config) throws ServletException {

        /*

         * nofilter = config.getInitParameter("excludes");

         * nofilterFiles =nofilter.split(","); sendRedirect =

         * config.getInitParameter("loginUrl");

         */

        // System.out.println(Arrays.asList(nofilterFiles));

    }

}