public class CharacterEncodingFilter implements Filter {private String charset;public void destroy() {// TODO Auto-generated method stub
        }public void doFilter(ServletRequest request, ServletResponse response,FilterChain filterChain) throws IOException, ServletException {// TODO Auto-generated method stub
        request.setCharacterEncoding(charset);filterChain.doFilter(request, response);}public void init(FilterConfig config) throws ServletException {// TODO Auto-generated method stubcharset = config.getInitParameter("charset");}}

<Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443"/>

public class CheckLoginFilter implements Filter {public void destroy() {// TODO Auto-generated method stub
        }public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {// TODO Auto-generated method stubHttpServletRequest hsRequest = (HttpServletRequest)request;HttpServletResponse hsResponse = (HttpServletResponse)response;HttpSession session = hsRequest.getSession();//没登录if(session.getAttribute("userID") == null){String uri = hsRequest.getRequestURI();// 请求登录页面if (uri.contains("log")||uri.contains("Log") || uri.contains("reg") || uri.contains("Reg")) {chain.doFilter(request, response);}else {// 请求其它页面hsResponse.sendRedirect("login.jsp");}}else {// 已登录,顺利跳转
            chain.doFilter(request, response);}}public void init(FilterConfig arg0) throws ServletException {// TODO Auto-generated method stub
}}

    <filter>   <filter-name>CharacterEncodingFilter</filter-name>   <filter-class>cn.guopeng.bbs.filter.CharacterEncodingFilter</filter-class> <init-param><param-name>charset</param-name><param-value>GBK</param-value></init-param></filter>   <filter-mapping>  <filter-name>CharacterEncodingFilter</filter-name>   <url-pattern>/*</url-pattern></filter-mapping><filter><filter-name>CheckLoginFilter</filter-name>   <filter-class>cn.guopeng.bbs.filter.CheckLoginFilter</filter-class>   </filter>   <filter-mapping>   <filter-name>CheckLoginFilter</filter-name>   <url-pattern>/*</url-pattern></filter-mapping>

（1）想过滤多个页面并且不全部过滤，

如果过滤或不过滤的地址比较有规律可以配置为全部过滤，然后在过滤器中编写代码只过滤一部分，其他的直接请求即可。

如果规律不明显，则只能通过web.xml配置，可以为过滤类写多个<filter-mapping>

（2）web.xml 中如果有servlet的配置信息， 那么filter应该在servlet的下面进行配置。