在项目中，过滤器如何配置？可以实现拦截！

package cn.itcast.crm.filter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
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 cn.itcast.crm.domain.SysUser;
import cn.itcast.crm.util.SessionUtils;
public class SessionCheckUserFilter implements Filter {
private List<String> list;
public void init(FilterConfig filterConfig) throws ServletException {
//自己处理放置在资源文件,利用流读入
list=new ArrayList<String>();
list.add("/image.jsp"); //验证码页面
list.add("/index.jsp");
list.add("/WEB-INF/page/login.jsp");
list.add("/sys/sysUserAction_isLogin.do");
}
public void doFilter(ServletRequest req, ServletResponse res,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest request=(HttpServletRequest)req;
HttpServletResponse response=(HttpServletResponse)res;
String path=request.getServletPath();

//对 /image.jsp  /index.jsp  /login.jsp   /sys/sysUserAction_isLogin路径过滤器要放行
if(list!=null&&list.contains(path)){
chain.doFilter(request, response);
return;
}

//获取当前的登陆用户
SysUser sysUser=SessionUtils.getSysUserFormSession(request);

//如果用户!=null 表示用户已经登陆
if(sysUser!=null){
//放行
chain.doFilter(request, response);
}else{  //如果用户==null 表示用户没有登陆
//重定向到login.jsp(index.jsp)
response.sendRedirect(request.getContextPath());
}
}

public void destroy() {

}

}

<?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"> 
<span style="color:#ff0000;"><filter>
<filter-name>SessionCheckUserFilter</filter-name>
<filter-class>cn.itcast.crm.filter.SessionCheckUserFilter</filter-class>
</filter>

<filter-mapping>
<filter-name>SessionCheckUserFilter</filter-name>
<url-pattern>*.jsp</url-pattern>
<dispatcher>REQUEST</dispatcher>
<dispatcher>FORWARD</dispatcher>
</filter-mapping>

<filter-mapping>
<filter-name>SessionCheckUserFilter</filter-name>
<url-pattern>*.do</url-pattern>
<dispatcher>REQUEST</dispatcher>
<dispatcher>FORWARD</dispatcher>
</filter-mapping></span>

<filter>
<filter-name>StrutsPrepareAndExecuteFilter</filter-name>
<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
</filter>

<filter-mapping>
<filter-name>StrutsPrepareAndExecuteFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>