简易sessionFilter

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>sp1</display-name>
  <filter>
      <filter-name>sessionFilter</filter-name>
      <filter-class>me.xuzs.sp1.web.filter.SessionFilter</filter-class>
      <init-param>
          <param-name>noFilterUrls</param-name>
          <param-value>/login/authn.jsp,/login/authnServlet</param-value>
      </init-param>
      <init-param>
          <param-name>redirectUrl</param-name>
          <param-value>/login/login.jsp</param-value>
      </init-param>
  </filter>
  <filter-mapping>
      <filter-name>sessionFilter</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>
  <servlet>
      <servlet-name>authnServlet</servlet-name>
      <servlet-class>me.xuzs.sp1.web.login.AuthnServlet</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>authnServlet</servlet-name>
      <url-pattern>/login/authnServlet</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

package me.xuzs.sp1.web.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;

public class SessionFilter implements Filter {
    
    /**
     * 不需要过滤的url
     */
    private String noFilterUrls;
    
    /**
     * 过滤后需要跳转的url
     */
    private String redirectUrl;
    
    /**
     * 当前的contextPath
     */
    private String contextPath;

    @Override
    public void destroy() {
        System.out.println("Session is destory.");
    }

    @Override
    public void doFilter(ServletRequest req, ServletResponse resp,
            FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;
        // 获取请求的url
        String url = String.valueOf(request.getRequestURI());
        HttpSession session = request.getSession(false);
        // 因为jsp默认会创建session，这里需双重判断
        if (null == session || null == session.getAttribute("userName")) {
            // 被跳转到的URL，直接放行
            if(url.equals(redirectUrl)){
                chain.doFilter(req, resp);
                return;
            }
            
            String[] notUrls = noFilterUrls.split(",");
            for (String s : notUrls) {
                if (url.equals(contextPath + s)) {
                    chain.doFilter(req, resp);
                    return;
                }
            }
            response.sendRedirect(redirectUrl);
            return;
        }
        chain.doFilter(req, resp);
    }

    @Override
    public void init(FilterConfig config) throws ServletException {
        System.out.println("Session is init.");
        noFilterUrls = config.getInitParameter("noFilterUrls");
        contextPath = config.getServletContext().getContextPath();
        redirectUrl = contextPath + config.getInitParameter("redirectUrl");
    }

}

可实现简单的session过滤！