实现Struts2中对未登录的jsp页面进行拦截功能（采用的是Struts2中过滤器进行过滤拦截）

	<filter>  
    <filter-name>SessionInvalidate</filter-name>  
    <filter-class>com.tp.action.SessionCheckFilter</filter-class>  //过滤器核心类的class地址
    <init-param>  
      <param-name>checkSessionKey</param-name>  //session中需要检查的key
      <param-value>users</param-value>  
    </init-param>  
    <init-param>  
      <param-name>redirectURL</param-name>  //过滤重定向的地址
      <param-value>/login.jsp</param-value>  
    </init-param>  
    <init-param>  
      <param-name>notCheckURLList</param-name>  //不需要过滤的jsp
      <param-value>/login.jsp</param-value>  
    </init-param>  
  </filter>  
  
  <filter-mapping>  
    <filter-name>SessionInvalidate</filter-name>  //需要过滤的文件
    <url-pattern>*.jsp</url-pattern>  
  </filter-mapping>  

package com.tp.action;
import java.io.IOException;  
import java.util.HashSet;  
import java.util.Set;  
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;  
/** 
 * 用于检测用户是否登陆的过滤器，如果未登录，则重定向到指的登录页面 配置参数 checkSessionKey 需检查的在 Session 中保存的关键字 
 * redirectURL 如果用户未登录，则重定向到指定的页面，URL不包括 ContextPath notCheckURLList 
 * 不做检查的URL列表，以分号分开，并且 URL 中不包括 ContextPath 
 */  
public class SessionCheckFilter implements Filter {  
  protected FilterConfig filterConfig = null;  
  private String redirectURL = null;  
  private Set<String> notCheckURLList = new HashSet<String>();  
  private String sessionKey = null;  
  @Override  
  public void destroy() {  
    notCheckURLList.clear();  
  }  
  @Override  
  public void doFilter(ServletRequest servletRequest,  
      ServletResponse servletResponse, FilterChain filterChain)  
      throws IOException, ServletException {  
    HttpServletRequest request = (HttpServletRequest) servletRequest;  
    HttpServletResponse response = (HttpServletResponse) servletResponse;  
    HttpSession session = request.getSession();  
    if (sessionKey == null) {  
      filterChain.doFilter(request, response);  
      return;  
    }  
    if ((!checkRequestURIIntNotFilterList(request))  
        && session.getAttribute("users") == null) {  
         response.sendRedirect(request.getContextPath() + redirectURL);  
      return;  
    }  
    filterChain.doFilter(servletRequest, servletResponse);  
  }  
  private boolean checkRequestURIIntNotFilterList(HttpServletRequest request) {  
    String uri = request.getServletPath()  
        + (request.getPathInfo() == null ? "" : request.getPathInfo());  
    String temp = request.getRequestURI();
    temp = temp.substring(request.getContextPath().length() + 1);  
    // System.out.println("是否包括："+uri+";"+notCheckURLList+"=="+notCheckURLList.contains(uri));  
    return notCheckURLList.contains(uri);  
  }  
  @Override  
  public void init(FilterConfig filterConfig) throws ServletException {  
    this.filterConfig = filterConfig;  
    redirectURL = filterConfig.getInitParameter("redirectURL");  
    sessionKey = filterConfig.getInitParameter("checkSessionKey");  
    String notCheckURLListStr = filterConfig  
        .getInitParameter("notCheckURLList");  
    if (notCheckURLListStr != null) {  
      System.out.println(notCheckURLListStr);  
      String[] params = notCheckURLListStr.split(",");  
      for (int i = 0; i < params.length; i++) {  
        notCheckURLList.add(params[i].trim());  
      }  
    }  
  }  
}